JP4889241B2 - Polypropylene heat shrinkable film - Google Patents

Description

  The present invention relates to a polypropylene-based heat-shrinkable film, and in particular, while maintaining the characteristics of a propylene-based heat-shrinkable film that has excellent heat resistance and excellent film appearance such as transparency and glossiness, stickiness, bleed-out and blocking The present invention relates to a polypropylene-based heat-shrinkable film that is safe even in the presence of thick corners due to its excellent handling, large heat shrinkage ratio, high impact resistance, and flexibility after shrinkage.

The heat-shrink film is widely used as an exterior for preventing the contents from being fouled, falsified, and improving display properties, or used for integrated packaging of products for improving transport efficiency and sales promotion.
Among these heat-shrinkable films (shrink films), polypropylene-based shrink films are characterized by high transparency and gloss, excellent appearance, and excellent heat resistance and rigidity.
Conventionally, as a polypropylene resin for a heat shrink film, a propylene-ethylene random copolymer has been mainly used from the viewpoint of transparency and shrinkage. However, conventional propylene-ethylene random copolymers use Ziegler-Natta catalysts for their production, and have a wide distribution in crystallinity and molecular weight, resulting in poor stickiness, blocking and bleedout, and shrinkage rate. Was not satisfactory.
In recent years, a method (patent document 1) using a crystalline propylene-α-olefin random copolymer having a specific thermal melting behavior with a narrow crystallinity and molecular weight distribution by a metallocene catalyst has been proposed. Bleed-out and the like are improved, and shrinkage characteristics are improved.

However, the conventional polypropylene-based shrink film is inferior in impact resistance, so it is not suitable for packaging heavy objects, etc., and because of its high rigidity, it cuts its hand when the corners of the bag become thick after shrinking. It sometimes caused problems.
For improving the impact resistance and imparting flexibility, a technique of blending a resin having excellent impact resistance such as an elastomer is generally used, and its use as a film is increasing.
Such blends are generally added at the time of molding, melt-kneaded in an extruder, or those in which polymerization is performed in multiple stages, but crystalline polypropylene is used in the first process and propylene is used in the second process. -The so-called block type reactor TPO, which produces ethylene copolymer elastomers, is characterized by superior heat resistance and productivity compared to random copolymer type elastomers, and mechanical mixing. Elastomers have advantages such as stable product quality, lower production costs, and a wide variety of elastomer compositions. ing.
However, most of them phase-separate the crystalline polypropylene produced in the first step and the propylene-ethylene copolymer elastomer produced in the second step, and the stretched film is not sufficiently transparent. There is a problem that the appearance of the product is impaired because the transparency after shrinkage is remarkably poor. Further, the phase separation tends to cause tearing from the interface, and it is difficult to say that the impact resistance is sufficient.
Therefore, even if a shrink film is manufactured using these raw materials, the required performance such as transparency cannot be sufficiently satisfied.

As an improvement in these resin raw materials, in order to improve flexibility and solve the deterioration of transparency, polypropylene or propylene-ethylene copolymer having a low ethylene content in the first step, and ethylene content in the second step There has been disclosed a technique in which a relatively small amount of propylene-ethylene copolymer elastomer, although more than the first step, is continuously polymerized using a Ziegler-Natta catalyst (Patent Document 2). However, because Ziegler-Natta catalysts have multiple types of active sites, the resulting propylene-ethylene copolymer has a wide crystallinity and molecular weight distribution, and produces many low-crystalline and low-molecular-weight components. Has strong stickiness and bleed-out (exudation of low molecular weight components and additives), which causes problems such as blocking and poor appearance and has problems in use as a product.
Furthermore, as an improvement in the resin raw material surface, a technique for increasing the intrinsic viscosity of the elastomer, that is, the molecular weight to a certain extent or more so as to suppress the formation of low molecular weight components has been disclosed (Patent Document 3). The generation of sexual components has a small inhibitory effect, transparency is not sufficient, improvement in stickiness and bleedout is still insufficient, and the appearance of defects such as spots and fish eyes due to the high molecular weight of the elastomer There are many problems that the film is liable to occur and the film is easily torn during stretch molding.

Japanese Patent Laid-Open No. 2001-240711 (Abstract and Claim 4) Japanese Patent Laid-Open No. 63-159212 (Claims, lower right column on page 2) JP-A-9-324022 (summary)

  As outlined in the background art, polypropylene heat-shrinkable films have not yet been able to satisfy all of transparency, heat resistance, stickiness, blocking resistance, impact resistance and flexibility. The object of the present invention is to maintain the characteristics of a polypropylene resin with excellent film appearance such as transparency and glossiness and high heat resistance, while being excellent in handling with less stickiness, bleed out, blocking, etc., and heat shrinkage Is to develop a polypropylene-based heat-shrinkable film having improved impact resistance, excellent impact resistance, excellent flexibility after shrinkage, and safe even with corners.

  The inventors of the present invention have previously had solid component viscoelastic characteristics, elution characteristics in temperature-elevated elution fractionation, etc., with specific component composition, molecular weight distribution, composition distribution, etc., by multistage polymerization using a metallocene catalyst. Although a series of research and development on the propylene-ethylene block copolymer is also carried out and an application has been filed as the previous invention (Japanese Patent Application No. 2003-371458 and others), various properties that are the problems of the present invention described above have been improved. In order to develop a polypropylene-based heat-shrinkable film, the invention of the prior application is used to effectively utilize the propylene ethylene block copolymer, which is a block type reactor TPO, as a film material. Using the propylene-ethylene block copolymer in the invention of the prior application as a raw material, the transparency and gloss While maintaining the characteristics of polypropylene resin with excellent film appearance and high heat resistance, there are few stickiness, bleed-out, blocking, etc., excellent handling, improved heat shrinkage ratio, excellent impact resistance, after shrinkage In order to realize a polypropylene heat-shrinkable film that is excellent in flexibility and safe even with corners, etc., a new method was sought.

  In order to find such a technique, the present inventors use a metallocene catalyst, and in the first step, more propylene-ethylene random copolymer component containing propylene alone or a small amount of ethylene in the second step than in the first step. In the propylene-ethylene block copolymer obtained by sequentially polymerizing propylene-ethylene random copolymer components containing ethylene, the component composition of each copolymer, ethylene content, crystallinity distribution and molecular weight distribution, Various considerations have been made regarding solid viscoelastic properties, elution characteristics in temperature-elevated elution fractionation methods, melt flow rates, melting peak temperatures measured by DSC, etc. In the process of performing, the requirements that can solve the above-described problems of the present invention can be newly recognized. This has led to the creation.

  Those basic requirements recognized as described above include, in the second step, a propylene-ethylene random copolymer component containing propylene alone or a small amount of ethylene in the first step using a metallocene catalyst. In the propylene-ethylene block copolymer obtained by sequentially polymerizing a propylene-ethylene random copolymer component containing more ethylene than in the first step, the component composition and ethylene content of each copolymer are specified, combined Thus, the tan δ curve is characterized as the melt flow rate and solid viscoelastic properties of the propylene-ethylene block copolymer, and the copolymer is used as a raw material for the polypropylene heat-shrinkable film.

Specifically, in the first step, propylene alone or propylene-ethylene random copolymer component (A1) having an ethylene content of 7 wt% or less is 30 to 95 wt%, and in the second step, 3 to 20 wt% more than component (A1). 70 to 5 wt% of the propylene-ethylene random copolymer component (A2) containing ethylene in a block copolymer, and in the block copolymer, the melt flow rate (MFR) is in the range of 0.1 to 30 g / 10 min. In order to improve the transparency of the film, in the temperature-loss tangent (tan δ) curve obtained by solid viscoelasticity measurement (DMA), the tan δ curve has a single peak at 0 ° C. or lower.
Such numerical definition is based on experimental verification and the like, and can be confirmed also by the comparison of Examples and Comparative Examples described later.

  The polypropylene-based heat-shrinkable film of the present invention is also used in the form of a multilayer film, and incidentally, the molecular weight obtained by gel permeation chromatography (GPC) measurement and the temperature by temperature-temperature elution fractionation method (TREF). The elution characteristic in the TREF elution curve obtained as a plot of elution amount (dWt% / dT) is also defined.

  In the above, the background of the creation of the present invention and the configuration and characteristics of the invention have been described in general. If the overall configuration of the present invention is viewed here, the present invention comprises the following invention unit groups. Note that the invention described in [1] is a basic invention, and [2] the following invention adds an additional requirement to the basic invention or shows an embodiment.

[1] Polypropylene heat shrinkage imparted with heat shrinkability by using a propylene-ethylene block copolymer satisfying the following conditions (Ai) to (A-iii) as a raw material and stretching in at least one direction Sex film.
(Ai) 30 to 95 wt% of propylene-ethylene random copolymer component (A1) having propylene alone or ethylene content of 7 wt% or less in the first step using the metallocene catalyst, and component (A1) in the second step It is a propylene-ethylene block copolymer obtained by successively polymerizing 70 to 5 wt% of a propylene-ethylene random copolymer component (A2) containing 3 to 20 wt% more ethylene than (A-ii) ) Melt flow rate (MFR: 2.16 kg 230 ° C.) is in the range of 0.1-30 g / 10 min (A-iii) Temperature-loss tangent (tan δ) curve obtained by solid viscoelasticity measurement (DMA) The tan δ curve has a single peak at 0 ° C. or lower. [2] A pro that satisfies the following conditions (Ai) to (A-iii) as a raw material Ren - comprising a layer with ethylene block copolymer at least one layer, heat-shrinkable multilayer polypropylene heat-shrinkable film has been granted by stretching in at least one direction.
(Ai) 30 to 95 wt% of propylene-ethylene random copolymer component (A1) having propylene alone or ethylene content of 7 wt% or less in the first step using the metallocene catalyst, and component (A1) in the second step It is a propylene-ethylene block copolymer obtained by successively polymerizing 70 to 5 wt% of a propylene-ethylene random copolymer component (A2) containing 3 to 20 wt% more ethylene than (A-ii) ) Melt flow rate (MFR: 2.16 kg 230 ° C.) is in the range of 0.1-30 g / 10 min (A-iii) Temperature-loss tangent (tan δ) curve obtained by solid viscoelasticity measurement (DMA) [3] The polypropylene-based heat-shrinkable film described in [1] or [2] In, propylene stretching - polypropylene heat-shrinkable film which comprises carrying out at a temperature 20 ° C. or more lower than the melting peak temperature measured by DSC of the ethylene block copolymer (A).
[4] A polypropylene heat-shrinkable film in which the polypropylene heat-shrinkable film made of the propylene-ethylene block copolymer described in any one of [1] to [3] is stretched at least uniaxially by a tenter method. Sex film.
[5] A polypropylene heat-shrinkable film obtained by biaxially stretching a polypropylene heat-shrinkable film using the propylene-ethylene block copolymer described in any one of [1] to [4]. the film.
[6] The polypropylene heat-shrinkable film according to any one of [1] to [5], wherein the propylene-ethylene block copolymer satisfies the following condition (A-iv).
(A-iv) The component amount W (Mw ≦ 5,000) of 5.000 or less in the molecular weight of the block copolymer obtained by gel permeation chromatography (GPC) measurement is 0.000 in the component (A). [7] The propylene-ethylene block copolymer satisfies the following conditions (Av) to (A-vi): [1] to [6] The polypropylene-based heat-shrinkable film described.
(Av) The component (A1) obtained in the first step is a propylene-ethylene random copolymer having an ethylene content in the range of 0.5 to 6 wt%, and the ratio in the whole is in the range of 30 to 85 wt%. Yes, the component (A2) obtained in the second step is a propylene-ethylene random copolymer containing 6 to 18 wt% more ethylene than (A1), and the total proportion is in the range of 70 to 15 wt% (A-vi) TREF obtained as a plot of elution amount (dWt% / dT) against temperature by temperature-elevated elution fractionation method (TREF) in the temperature range of −15 ° C. to 140 ° C. using o-dichlorobenzene solvent In the elution curve, the peak T (A1) observed on the high temperature side is in the range of 55 ° C. to 96 ° C., and the peak T (A2) observed on the low temperature side is below 45 ° C. Or the peak T (A2) is not observed, and the temperature T (A4) at which 99 wt% of the total propylene-ethylene block copolymer elutes is 98 ° C. or lower. [8] Propylene-ethylene block copolymer (A ) Satisfies the following conditions (A-vii) to (A-iii): The polypropylene heat-shrinkable film according to any one of [1] to [7].
(A-vii) The component (A1) obtained in the first step is a propylene-ethylene random copolymer having an ethylene content in the range of 1.5 to 6 wt%, and the ratio in the whole is in the range of 30 to 70 wt%. Yes, the component (A2) obtained in the second step is a propylene-ethylene random copolymer containing 8 to 16 wt% more ethylene than (A1), and the ratio in the whole is in the range of 70 to 30 wt% (A-ix) TREF obtained as a plot of elution amount (dWt% / dT) against temperature by the temperature rising elution fractionation method (TREF) in the temperature range of -15 ° C to 140 ° C using o-dichlorobenzene solvent In the elution curve, the peak T (A1) observed on the high temperature side is in the range of 60 ° C. to 88 ° C., and the peak T (A2) observed on the low temperature side is below 40 ° C. , Or peak T (A2) is not observed, the total propylene - the temperature T to 99 wt% of the ethylene block copolymer is eluted (A4) is 90 ° C. or less

  The polypropylene-based heat-shrinkable film in the present invention is excellent in film appearance such as transparency and gloss, has high heat resistance, has little stickiness, bleed-out, blocking, etc., is easy to handle, has a large heat shrinkage rate, and has an impact resistance. Even if there is a thickened corner because it is highly flexible and flexible after contraction, it is safe.

1. Configuration of Propylene-Ethylene Block Copolymer (1) Basic Rules In the present invention, the propylene-ethylene block copolymer used as a raw material for the polypropylene heat-shrinkable film is propylene in the first step using a metallocene catalyst. A propylene-ethylene random copolymer component containing 30 to 95 wt% of propylene-ethylene random copolymer component (A1) alone or having an ethylene content of 7 wt% or less and 3 to 20 wt% more ethylene than the first step in the second step It is obtained by successively polymerizing 70 to 5 wt% of the component (A2).
Such a propylene-ethylene block copolymer is commonly called a so-called block copolymer, but is in a blended state of component (A1) and component (A2), and both are bonded by polymerization. It is not what you have.

(2) Component (A1) (2-1) Ethylene content E in component (A1) E (A1)
The component (A1) produced in the first step is a propylene homopolymer having a relatively high melting point and crystallinity, or propylene having an ethylene content of 7 wt% or less in order to suppress stickiness and develop heat resistance. -It must be an ethylene random copolymer. When the ethylene content exceeds 7 wt%, the melting point becomes too low and the heat resistance is deteriorated, so the ethylene content is 7 wt% or less, preferably 6 wt% or less.
The component (A1) exhibits improved flexibility, transparency and heat resistance even with a propylene homopolymer, but sufficient flexibility while maintaining transparency when the component (A1) is a propylene homopolymer. It is necessary to increase the proportion of the component (A2) described later in order to exhibit the above, and there is a concern that the heat resistance and remarkable deterioration such as stickiness and blocking may be caused.
On the other hand, when the component (A1) is a propylene-ethylene random copolymer, the heat resistance seems to deteriorate due to a decrease in the melting point of the component (A1) itself, but it is necessary for exhibiting sufficient flexibility. Since the amount of the component (A2) can be suppressed, the heat resistance of the block copolymer as a whole is rather improved, and stickiness and blocking are less deteriorated, which is preferable.
Further, by reducing the melting point, a heat-shrinkable film having extremely excellent heat-shrinkage performance can be obtained by obtaining sufficient molding stability even when the molding temperature during stretch molding is lowered.
From these viewpoints, the ethylene content in the component (A1) is preferably 0.5 wt% or more, more preferably 1.5 wt% or more.

(2-2) Proportion of component (A1) in block copolymer If the proportion of component (A1) in propylene-ethylene block copolymer is too large, the flexibility and resistance of propylene-ethylene block copolymer The effect of improving impact properties and transparency cannot be exhibited sufficiently. Therefore, the ratio of the component (A1) is 95 wt% or less, preferably 85 wt% or less, more preferably 70 wt% or less.
On the other hand, if the proportion of the component (A1) becomes too small, the stickiness increases and the heat resistance is remarkably deteriorated.

(3) About component (A2) (3-1) Ethylene content E (A2) in component (A2)
The propylene-ethylene random copolymer component (A2) produced in the second step is a component necessary for improving the flexibility, impact resistance and transparency of the propylene-ethylene block copolymer (A). .
Here, the component (A2) needs to have an ethylene content in a specific range in order to sufficiently exhibit the above effects. That is, in the block copolymer of the present invention, the lower the crystallinity of the component (A2) relative to the component (A1), the greater the flexibility improvement effect, and the crystallinity is the ethylene content in the propylene-ethylene random copolymer. Therefore, the ethylene content E (A2) in the component (A2) cannot be effective unless the ethylene content E (A1) in the component (A1) is 3 wt% or more, preferably 6 wt%. % Or more, more preferably 8 wt% or more, and more ethylene than component (A1).
Here, when the difference in ethylene content between the component (A1) and the component (A2) is defined as E (gap) (= E (A2) −E (A1)), E (gap) is 3 wt% or more, preferably 6 wt% % Or more, more preferably 8 wt% or more.
On the other hand, if the ethylene content is excessively increased to lower the crystallinity of the component (A2), the difference E (gap) between the ethylene content of the component (A1) and the component (A2) increases, and the phase is divided into a matrix and a domain. A separation structure is taken, and transparency is lowered. This is because polypropylene originally has low compatibility with polyethylene, and even in the propylene-ethylene random copolymer, although the ethylene content is different, the mutual compatibility decreases as the difference in ethylene content increases. The upper limit of E (gap) may be in a range where the peak of tan δ becomes single by solid viscoelasticity measurement described later in paragraph 0025. For that purpose, E (gap) is 20 wt% or less, preferably 18 wt%. % Or less, more preferably 16 wt% or less.

(3-2) Proportion of component (A2) in block copolymer If the proportion of component (A2) is too large, stickiness will increase and blocking will be deteriorated, and the heat resistance will be significantly reduced. The ratio of A2) needs to be suppressed to 70 wt% or less.
On the other hand, if the proportion of component (A2) becomes too small, the effect of improving flexibility and impact resistance cannot be obtained, so the proportion of (A2) needs to be 5 wt% or more, preferably 15 wt% or more. More preferably, it is 30 wt% or more.

(4) Melt flow rate (MFR) of block copolymer
The MFR of the propylene-ethylene random copolymer used for the polypropylene film of the present invention needs to be in the range of 0.1 to 30 g / 10 min. In the present invention, if the MFR is too low, surface roughness called shark skin or melt fracture melt fracture occurs on the surface of the film, which not only significantly deteriorates transparency and appearance but also makes stretch molding difficult. On the other hand, if the MFR is too high, the shrinkage rate and impact resistance are lowered, which is not preferable.
Therefore, in the present invention, the MFR of the component (A) must be in the range of 0.1 to 30 g / 10 min, and the range of 0.5 to 10 g / 10 min is the balance of molding stability, film appearance, and physical properties. It is preferable from the viewpoint.
The melt flow rate (MFR) in the present invention is measured under the conditions of test temperature: 230 ° C. nominal load: 2.16 kg, die shape: 2.095 mm in diameter, and 8.00 mm in length according to JIS K7210 A method condition M. It is.

(5) Specification by solid viscoelasticity (5-1) Specification by peak of tan δ curve In the propylene-ethylene block copolymer used for the polypropylene film of the present invention, temperature obtained by solid viscoelasticity measurement (DMA)- In the loss tangent (tan δ) curve, it is necessary that the tan δ curve has a single peak below 0 ° C.
When the component propylene-ethylene block copolymer has a phase separation structure, the glass transition temperature of the amorphous part contained in the component (A1) is different from the glass transition temperature of the amorphous part contained in the component (A2). Therefore, there are a plurality of peaks. In this case, there arises a problem that the transparency is remarkably deteriorated.
Whether or not the phase separation structure is taken can be discriminated in the tan δ curve in the measurement of solid viscoelasticity. Is brought about by having.
In the present invention, it is necessary that the tan δ curve in the solid viscoelasticity measurement has a single peak in order to exhibit transparency.
In addition, the example of the peak of the tan-delta curve of this invention and the example of the tan-delta curve when it does not have a single peak for comparison are shown in FIG. 2 and FIG. It is shown.

(5-2) Measurement method Specifically, solid viscoelasticity measurement is performed by applying a sinusoidal strain of a specific frequency to a strip-shaped sample piece and detecting the generated stress. Here, the frequency is 1 Hz, and the measurement temperature is raised stepwise from −60 ° C. until the sample is melted and cannot be measured. Further, it is recommended that the magnitude of distortion is about 0.1 to 0.5%. From the obtained stress, the storage elastic modulus and the loss elastic modulus are obtained by a known method, and the loss tangent (= loss elastic modulus G ″ / storage elastic modulus G ′) defined by the ratio is plotted against the temperature. Then, a tan δ curve is obtained, and in the present invention, a sharp peak is shown in a temperature range of 0 ° C. or lower. Generally, the peak of the tan δ curve at 0 ° C. or lower is for observing the glass transition of the amorphous part, and here, this peak temperature is defined as the glass transition temperature Tg (° C.).

(6) Specificity of ethylene content E (A1) and E (A2) and component amounts W (A1) and W (A2) of components (A1) and (A2) of components (A1) and (A2) Each ethylene content and component amount can be specified by the material balance at the time of polymerization (material balance), but in order to specify these more accurately, it is desirable to use the following analysis (fractionation method). .

(6-1) Identification of each component amount W (A1) and W (A2) by temperature rising elution fractionation method (TREF) 6-1-1. Temperature Elevated Elution Fractionation Method A technique for evaluating the crystalline distribution of propylene-ethylene random copolymer by temperature elevated elution fractionation method (TREF) is well known to those skilled in the art. Detailed measurement methods are shown.
G. Glockner, J. et al. Appl. Polym. Sci. : Appl. Polym. Symp. 45, 1-24 (1990)
L. Wild, Adv. Polym. Sci. 98, 1-47 (1990)
J. et al. B. P. Soares, A .; E. Hamielec, polymer; 36, 8, 1639-1654 (1995)
The propylene-ethylene block copolymer in the present invention is greatly different in the crystallinity of each of the components (A1) and (A2), and each crystallinity distribution is narrow by being produced using a metallocene catalyst. Therefore, there are very few intermediate components between the two, and both can be accurately separated by TREF.

In the TREF elution curve obtained as a plot of elution amount (dWt% / dT) against temperature by the temperature rising elution fractionation method (TREF) in the temperature range of −15 ° C. to 140 ° C. using o-dichlorobenzene solvent, (A1) and (A2) show their elution peaks at the respective temperatures T (A1) and T (A2) due to the difference in crystallinity, and since the difference is sufficiently large, the intermediate temperature T (A3) (= {T Separation is almost possible at (A1) + T (A2)} / 2).
In addition, the lower limit of the TREF measurement temperature is −15 ° C. in the apparatus used for this measurement, but in the case where the crystallinity of the component (A2) is very low or an amorphous component, There may be no peak within the range (at this time, the concentration of the component (A2) dissolved in the solvent is detected at the lower limit of the measurement temperature (ie, −15 ° C.)). In this case, T (A2) is considered to exist below the lower limit of the measurement temperature, but the value cannot be measured. In such a case, T (A2) is the lower limit of the measurement temperature − It is defined as 15 ° C.
Here, if the integrated amount of the component eluted before T (A3) is defined as W (A2) wt%, and the integrated amount of the component eluted at T (A3) or higher is defined as W (A1) wt%, W (A2) Almost corresponds to the amount of the low-crystalline or amorphous component (A2), and the integrated amount W (A1) of the component eluted at T (A3) or higher is the component (A1) having a relatively high crystallinity. Almost corresponds to the amount of. In addition, the example of a TREF elution curve is illustrated by FIG. 1 as an example in superposition | polymerization manufacture example A-1.

6-1-2. TREF Measurement Method In the present invention, specifically, measurement is 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, a component of -15 ° C o-dichlorobenzene (containing 0.5 mg / ml BHT), which is a solvent, flows through the column at a flow rate of 1 ml / min, and is dissolved in -15 ° C o-dichlorobenzene in the TREF column. Is eluted for 10 minutes, and then the column is linearly heated to 140 ° C. at a heating rate of 100 ° C./hour to obtain an elution curve.

(6-2) Determination of ethylene content E (A1) and E (A2) in each component 6-2-1. Separation of components (A1) and (A2) Based on T (A3) determined by the previous TREF measurement, the component of the soluble component in T (A3) (by temperature rising column fractionation using a preparative fractionator ( A2) and the insoluble component (A1) in T (A3) are fractionated, and the ethylene content of each component is determined by NMR.
The temperature rising column fractionation method is a measurement method disclosed in, for example, Macromolecules 21 314-319 (1988). Specifically, the following method was used in the present invention.

6-2-2. Fractionation conditions A cylindrical column having a diameter of 50 mm and a height of 500 mm is filled with a glass bead carrier (80 to 100 mesh) 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 (A3) 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 (A3), 800 ml of o-dichlorobenzene of T (A3) is allowed to flow at a flow rate of 20 ml / min, whereby components soluble in T (A3) present in the column are 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. , T (A3) is eluted and recovered.
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.

6-2-3. ¹³ C-NMR by measuring the fractionated by components obtained ethylene content and (A1) (A2) an ethylene content of each was measured according to the following conditions by complete proton decoupling ^method, a 13 C-NMR spectrum Obtained by analysis.
Model: GSX-400 manufactured by JEOL Ltd. or equivalent device (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 attributions measured under the above conditions are shown in Table 1. In the table, symbols such as S _αα 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 types of triads of PPP, PPE, EPE, PEP, PEE, and EEE may exist in the chain. As described in Macromolecules 15 1150 (1982) and the like, 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 (T _ββ ) (1)
[PPE] = k × I (T _βδ ) (2)
[EPE] = k × I (T _δδ ) (3)
[PEP] = k × I (S _ββ ) (4)
[PEE] = k × I (S _ββ ) (5)
[EEE] = k × {I (S _δδ ) / 2 + I (S _γδ ) / 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 (T _ββ ) means the intensity of the peak at 28.7 ppm attributed to T _ββ .
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 of the present invention contains a small amount of a propylene hetero bond (2,1-bond and / or 1,3-bond), thereby producing a minute peak shown in Table 2.

In order to obtain an accurate ethylene content, it is necessary to include these peaks derived from heterogeneous bonds in the calculation, but it is difficult to completely separate and identify the peaks derived from heterogeneous bonds, and the amount of heterogeneous bonds is small. Therefore, the ethylene content of the present invention is obtained by 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. I will do it.
Conversion from mol% to wt% of ethylene content is performed using the following formula.
Ethylene content (% by weight) = (28 × X / 100) / {28 × X / 100 + 42 × (1− × / 100)} × 100 where X is the ethylene content in mol%.
Further, the ethylene content E (W) of the entire block copolymer is calculated from the ethylene contents E (A1), E (A2) and TREF of the components (A1) and (A2) measured above. The weight ratio W (A1) and W (A2) wt% is calculated by the following formula.
E (W) = {E (A1) × W (A1) + E (A2) × W (A2)} / 100 (wt%)

(6-3) Additional requirement of crystallinity distribution by TREF elution curve By using the TREF elution curve used for specifying the amount of each component, the propylene-ethylene block copolymer of the present invention has a crystallinity distribution. Additional features can be found in
6-3-1. Elution peak temperature T (A1)
The higher the elution peak temperature T (A1) of the component (A1) in the TREF elution curve, the higher the crystallinity of the component (A1). At this time, the higher the crystallinity of the component (A1), the higher the propylene-ethylene block content. The component (A2) necessary to improve the impact resistance of the polymer and the flexibility after shrinkage must be increased.
On the other hand, if the proportion of the component (A2) becomes too large, stickiness, blocking deterioration and heat resistance decrease occur. In order to improve the balance between impact resistance and flexibility after shrinkage, transparency, T (A1) should not be too high. Furthermore, although the heat shrinkage rate tends to deteriorate with an increase in the stretching temperature, it is preferable in that T (A1) is lowered so that stable molding is possible even when the stretching temperature is lowered.
In the present invention, component (A1) is propylene alone or a random copolymer of ethylene of 7 wt% or less, but T (A1) can be decreased by increasing the ethylene content. At this time, in order to exhibit sufficient balance between flexibility, transparency, and heat resistance, T (A1) is preferably 96 ° C. or lower, and most preferably in the range of 88 ° C. or lower.
On the other hand, when the peak temperature T (A1) is less than 55 ° C., the temperature at which the component (A1) crystals melt is low, and the block copolymer cannot exhibit sufficient heat resistance, resulting in poor blocking. Therefore, in the present invention, the peak temperature T (A1) is preferably 55 ° C. or higher, and more preferably 60 ° C. or higher.

6-3-2. Elution end temperature T (A4)
Even if T (A1) is low, transparency is deteriorated when the crystallinity distribution is present on the high crystal side. Furthermore, there arises a problem that it becomes difficult to lower the stretching temperature described later. This is presumed to be caused by having a crystalline distribution on the high crystal side and making uniform stretching difficult during stretching. Therefore, it is preferable that the crystallinity spread to the high temperature side is suppressed in the TREF elution curve. The spread of crystallinity toward the high crystal side can be evaluated by TREF measurement, and the elution end temperature T (A4) of the entire component propylene-ethylene block copolymer with respect to the peak temperature T (A1) (however, TREF measurement Since it is difficult to define the temperature at which all elution occurs, it is preferable that the temperature at which 99 wt% of the elution is defined as the elution end temperature T (A4) is not high in the present invention. If there is an elution component on the side, the crystallinity of the component increases. Therefore, as a preferable requirement of the present invention, T (A4) is 98 ° C. or less, preferably 90 ° C. or less.
Furthermore, the temperature difference ΔT (T (A4) −T (A1)) from the elution peak to the end is preferably 5 ° C. or less, more preferably 4 ° C. or less, and even more preferably 3 ° C. or less.

6-3-3. Elution peak temperature T (A2)
If the crystallinity of the component (A2) is not sufficiently lowered, the flexibility and transparency of the propylene-ethylene block copolymer component (A) cannot be ensured, so T (A2) is preferably 45 ° C. or lower. More preferably, it is 40 ° C. or lower.

(7) Regarding molecular weight (7-1) Regulation of molecular weight The propylene-ethylene block copolymer component (A) in the present invention is additionally characterized by a low amount of low molecular weight components.
It is considered that a low molecular weight component, particularly a component whose molecular weight is less than the molecular weight between the entanglement points, bleeds out to the surface of the molded body and deteriorates stickiness and transparency.
The molecular weight between the entanglement points of polypropylene is about 5,000, as described in Journal of Polymer Science: Part B: Polymer Physics; 37 1023-1103 (1999).
Therefore, the block copolymer in the present invention has a low molecular weight component and the amount of the component having a weight average molecular weight of 5,000 or less is 0.6 wt% or less, preferably 0.4 wt% or less.

(7-2) Molecular weight measurement In this invention, a weight average molecular weight (Mw) and a number average molecular weight (Mn) say what was measured by the gel permeation chromatography (GPC) method.
Conversion from the retention volume to the molecular weight is performed using a calibration curve prepared in advance with standard polystyrene.
Standard polystyrenes used are the following brands manufactured by Tosoh Corporation. F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, A1000
A calibration curve is prepared by injecting 0.2 ml of a solution dissolved in o-dichlorobenzene (containing 0.5 mg / ml BHT) so that each is 0.5 mg / ml. The calibration curve uses a cubic equation obtained by approximation by the least square method. The following numerical value is used for [η] = K × M ^α in the viscosity formula used for conversion to molecular weight.
PS: K = 1.38 × 10 ⁻⁴ α = 0.7
PE: K = 3.92 × 10 ⁻⁴ α = 0.733
PP: K = 1.03 × 10 ⁻⁴ α = 0.78
The measurement conditions for GPC are as follows.
Apparatus: GPC (ALC / GPC 150C) manufactured by WATERS
Detector: MIRAN 1A IR detector manufactured by FOXBORO (measurement wavelength: 3.42 μm)
Column: AD806M / S (3 pieces) manufactured by Showa Denko KK
Mobile phase solvent: o-dichlorobenzene Measurement temperature: 140 ° C.
Flow rate: 1.0 ml / min
Injection volume: 0.2ml
Sample Preparation Prepare a 1 mg / ml solution using o-dichlorobenzene (containing 0.5 mg / ml BHT) and dissolve it at 140 ° C. for about 1 hour.
The amount of the component having a molecular weight of 5,000 or less can also be determined from a plot of the elution ratio with respect to the molecular weight obtained by GPC measurement.

2. Propylene-ethylene block polymer production method (1) Metallocene catalyst The method for producing the propylene-ethylene block copolymer (A) of the present invention requires the use of a metallocene catalyst.
It is well known to those skilled in the art that stickiness and bleedout deteriorate when the molecular weight and crystallinity distribution are wide in the propylene-ethylene block copolymer, but also in the propylene-ethylene block copolymer used in the present invention, In order to suppress stickiness and bleed out, and to exhibit sufficient transparency and heat shrinkability in a heat shrinkable film, it is necessary to polymerize using a metallocene catalyst that can narrow the molecular weight and crystallinity distribution. It is apparent from the comparison of the examples and comparative examples described later that the Ziegler-Natta catalyst does not yield the excellent propylene-ethylene block copolymer of the present invention.

  The type of the metallocene-based catalyst is not particularly limited as long as it can produce a copolymer having the performance of the present invention. However, in order to satisfy the requirements of the present invention, for example, the following components ( It is preferable to use a metallocene catalyst comprising a) and (b) and, if necessary, the component (c) used.

Component (a): At least one metallocene transition metal compound selected from the transition metal compounds represented by the general formula (1) Component (b): At least one selected from the following (b-1) to (b-4) (B-1) an ionic compound capable of reacting with the component (A) to convert the component (A) into a cation, or (B-3) Solid acid fine particles (b-4) Ion exchange layered silicate component (c): Organoaluminum compound.

(1-1) Component (a)
As the component (a), at least one metallocene transition metal compound selected from transition metal compounds represented by the following general formula (1) can be used.
_{Q (C 5 H 4 -aR 1} ) (C 5 H 4 -bR 2) MeXY (1)
[Wherein Q represents a divalent linking group that bridges two conjugated five-membered ring ligands, Me represents a metal atom selected from titanium, zirconium, and hafnium, and X and Y represent hydrogen atoms. Atom, halogen atom, hydrocarbon group, alkoxy group, amino group, nitrogen-containing hydrocarbon group, phosphorus-containing hydrocarbon group or silicon-containing hydrocarbon group, X and Y are each independently, ie, the same or different. Also good. R ₁ and R ₂ represent hydrogen, a hydrocarbon group, a halogenated hydrocarbon group, a silicon-containing hydrocarbon group, a nitrogen-containing hydrocarbon group, an oxygen-containing hydrocarbon group, a boron-containing hydrocarbon group, or a phosphorus-containing hydrocarbon group. . a and b are the number of substituents. ]

Specifically, Q represents a divalent linking group that bridges two conjugated five-membered ring ligands, and has, for example, a divalent hydrocarbon group, a silylene group or an oligosilylene group, or a hydrocarbon group as a substituent. Examples include a silylene group, an oligosilylene group, or a germylene group having a hydrocarbon group as a substituent. Among these, preferred is a silylene group having a divalent hydrocarbon group and a hydrocarbon group as a substituent.
X and Y represent a hydrogen atom, a halogen atom, a hydrocarbon group, an alkoxy group, an amino group, a nitrogen-containing hydrocarbon group, a phosphorus-containing hydrocarbon group, or a silicon-containing hydrocarbon group. Among these, hydrogen is preferable , Chlorine, methyl, isobutyl, phenyl, dimethylamide, diethylamide group and the like. X and Y may be independent, that is, may be the same or different.
R ₁ and R ₂ represent hydrogen, a hydrocarbon group, a halogenated hydrocarbon group, a silicon-containing hydrocarbon group, a nitrogen-containing hydrocarbon group, an oxygen-containing hydrocarbon group, a boron-containing hydrocarbon group, or a phosphorus-containing hydrocarbon group. . Specific examples of the hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a phenyl group, a naphthyl group, a butenyl group, and a butadienyl group. In addition, halogenated hydrocarbon group, silicon-containing hydrocarbon group, nitrogen-containing hydrocarbon group, oxygen-containing hydrocarbon group, boron-containing hydrocarbon group or phosphorus-containing hydrocarbon group include methoxy group, ethoxy group, phenoxy group, trimethylsilyl group. Typical examples include a group, diethylamino group, diphenylamino group, pyrazolyl group, indolyl group, dimethylphosphino group, diphenylphosphino group, diphenylboron group, dimethoxyboron group and the like. In these, it is preferable that it is a C1-C20 hydrocarbon group, and it is especially preferable that they are a methyl group, an ethyl group, a propyl group, and a butyl group. By the way, adjacent R ₁ and R ₂ may combine to form a ring, on which a hydrocarbon group, halogenated hydrocarbon group, silicon-containing hydrocarbon group, nitrogen-containing hydrocarbon group, oxygen-containing You may have a substituent which consists of a hydrocarbon group, a boron containing hydrocarbon group, or a phosphorus containing hydrocarbon group.
Me is a metal atom selected from titanium, zirconium and hafnium, preferably zirconium and hafnium.

  Among the components (a) described above, preferred for the production of the propylene polymer of the present invention is a substituted cyclopentadienyl group crosslinked with a silylene group, a germylene group or an alkylene group having a hydrocarbon substituent. A transition metal compound comprising a ligand having a substituted indenyl group, a substituted fluorenyl group, or a substituted azulenyl group, particularly preferably a 2,4-position crosslinked by a silylene group having a hydrocarbon substituent or a germylene group It is a transition metal compound comprising a ligand having a substituted indenyl group and a 2,4-position substituted azulenyl group.

Non-limiting specific examples include dimethylsilylene bis (2-methyl-4-phenylindenyl) zirconium dichloride, diphenylsilylene bis (2-methyl-4-phenylindenyl) zirconium dichloride, dimethylsilylene bis (2-methyl). Benzoindenyl) zirconium dichloride, dimethylsilylenebis {2-isopropyl-4- (3,5-diisopropylphenyl) indenyl} zirconium dichloride, dimethylsilylenebis (2-propyl-4-phenanthrylindenyl) zirconium dichloride, dimethyl Silylene bis (2-methyl-4-phenylazurenyl) zirconium dichloride, dimethylsilylene bis {2-methyl-4- (4-chlorophenyl) azurenyl} zirconium dichloride, dimethylsilylene bi (2-Ethyl-4-phenylazurenyl) zirconium dichloride, dimethylsilylenebis (2-isopropyl-4-phenylazurenyl) zirconium dichloride, dimethylsilylenebis {2-ethyl-4- (2-fluorobiphenyl) azurenyl} zirconium Examples thereof include dichloride and dimethylsilylenebis {2-ethyl-4- (4-t-butyl-3-chlorophenyl) azurenyl} zirconium dichloride.
A compound in which the silylene group of these specific examples is replaced with a germylene group and zirconium is replaced with hafnium is also exemplified as a suitable compound.
In addition, since the catalyst component is not an important element of the present invention, it avoids complicated listing and is limited to a representative example, but it is obvious that the effective range of the present invention is not limited thereby. It is.

(1-2) Component (b)
As the component (b), at least one solid component selected from the components (b-1) to (b-4) described above is used. Each of these components is a known component, and can be appropriately selected from known technologies and used. Specific examples and manufacturing methods thereof are described in detail in JP-A No. 2002-284808, JP-A No. 2002-53609, JP-A No. 2002-69116, JP-A No. 2003-105015, and the like.
Here, as the particulate carrier used for the component (b-1) and the component (b-2), inorganic oxides such as silica, alumina, magnesia, silica alumina, silica magnesia, magnesium chloride, magnesium oxychloride, chloride Examples thereof include inorganic halides such as aluminum and lanthanum chloride, and porous organic carriers such as polypropylene, polyethylene, polystyrene, styrene divinyl benzene copolymer, and acrylic acid copolymer.

Further, as a non-limiting specific example of the component (B), a particulate carrier on which methylalumoxane, isobutylalumoxane, methylisobutylalumoxane, aluminum butylboronate tetraisobutyl, etc. are supported as the component (b-1). As component (b-2), triphenylborane, tris (3,5-difluorophenyl) borane, tris (pentafluorophenyl) borane, triphenylcarbonium tetrakis (pentafluorophenyl) borate, N, N-dimethyl Particulate carrier carrying anilinium tetrakis (pentafluorophenyl) borate, etc., component (b-3), alumina, silica alumina, magnesium chloride, etc., component (b-4), montmorillonite, zakonite, beidellite , Nontronic , Saponite, hectorite, stevensite, bentonite, smectite group such as taeniolite, vermiculite, and the like mica group. These may form a mixed layer.
Particularly preferred among the above components (b) is the ion-exchange layered silicate of component (b-4), and more preferred are chemical treatments such as acid treatment, alkali treatment, salt treatment, and organic matter treatment. It is an ion exchange layered silicate applied.

(1-3) Component (c)
Examples of organoaluminum compounds used as component (c) as needed are:
General formula AIR _a X _3-a
(Wherein R is a hydrocarbon group having 1 to 20 carbon atoms, X is hydrogen, halogen, alkoxy group, a is a number of 0 <a ≦ 3), trimethylaluminum, triethylaluminum, tripropylaluminum, Trialkylaluminum such as triisobutylaluminum or halogen- or alkoxy-containing alkylaluminum such as diethylaluminum monochloride, diethylaluminum monomethoxide. In addition, aluminoxanes such as methylaluminoxane can also be used. Of these, trialkylaluminum is particularly preferred.

(1-4) Formation of catalyst Component (a), component (b) and, if necessary, component (c) are brought into contact to form a catalyst. The contact method is not particularly limited, but the contact can be made in the following order. Moreover, this contact may be performed not only at the time of catalyst preparation but also at the time of prepolymerization with olefin or at the time of polymerization of olefin.
1) Contact component (a) and component (b) 2) Add component (c) after contacting component (a) and component (b) 3) Contact component (a) and component (c) 4) Add component (b) after contact 4) Add component (a) after contacting component (b) and component (c) 5) Contact three components simultaneously

(1-5) Component Amounts The amounts of components (a), (b) and (c) used in the present invention are arbitrary. For example, the amount of component (a) used relative to component (b) is preferably in the range of 0.1 μmol to 1.000 μmol, particularly preferably 0.5 μmol to 500 μmol, relative to 1 g of component (b). The amount of component (c) used relative to component (b) is preferably such that the amount of transition metal is 0.001 to 100 μmol, particularly preferably 0.005 to 50 μmol, relative to 1 g of component (b). Therefore, the amount of the component (c) to the component (a) is preferably in the range of 10 ⁻⁵ to 50, particularly preferably 10 ^{−4 to} 5 in terms of the molar ratio of the transition metal.

(1-6) Prepolymerization It is preferable that the catalyst of the present invention is subjected to a prepolymerization treatment in which a small amount of the olefin is previously brought into contact with the catalyst. The olefin to be used is not particularly limited, but ethylene, propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane, styrene and the like can be used. It is possible to use, and it is particularly preferable to use propylene. The olefin can be supplied by any method such as a supply method for maintaining the olefin at a constant speed or in a constant pressure state, a combination thereof, or a stepwise change. The prepolymerization temperature and time are not particularly limited, but are preferably in the range of −20 ° C. to 100 ° C. and 5 minutes to 24 hours, respectively. The amount of prepolymerization is preferably 0.01 to 100, more preferably 0.1 to 50 with respect to the component (b). After completion of the prepolymerization, the catalyst can be used as it is, depending on the usage form of the catalyst, but may be dried if necessary.
Furthermore, a polymer such as polyethylene, polypropylene, or polystyrene, or an inorganic oxide solid such as silica or titania can be allowed to coexist during or after the contact of the above components.

(2) Production method (2-1) Sequential polymerization In producing the propylene-ethylene block polymer (A) of the present invention, the crystalline propylene-ethylene random copolymer component (A1) and low crystalline or non-crystalline The crystalline propylene-ethylene random copolymer component (A2) needs to be sequentially polymerized for the reason described above.
When performing sequential polymerization, either a batch method or a continuous method can be used, but it is generally desirable to use a continuous method from the viewpoint of productivity.
In the case of a batch method, it is possible to polymerize component (A1) and component (A2) separately using a single reactor by changing the polymerization conditions with time. As long as the effects of the present invention are not impaired, a plurality of reactors may be connected in parallel.
In the case of the continuous method, it is necessary to use a production facility in which two or more reactors are connected in series because it is necessary to individually polymerize the component (A1) and the component (A2), but as long as the effect of the present invention is not impaired. A plurality of reactors may be connected in series and / or in parallel for each of component (A1) and component (A2).

(2-2) Polymerization process As the polymerization process (polymerization method), an arbitrary polymerization method such as a slurry method, a bulk method, or a gas phase method can be used. Although supercritical conditions can be used as intermediate conditions between the bulk method and the gas phase method, they are substantially the same as the gas phase method, and are therefore included in the gas phase method without particular distinction.
Since the low crystalline or amorphous propylene-ethylene random copolymer component (A2) is easily soluble in organic solvents such as hydrocarbons and liquefied propylene, it is desirable to use a gas phase method for the production of the component (A2).
Any process may be used for the production of the crystalline propylene-ethylene random copolymer component (A1), but in the case of producing the component (A1) having a relatively low crystallinity, adhesion, etc. In order to avoid this problem, it is desirable to use a vapor phase method.
Therefore, the crystalline propylene-ethylene random copolymer component (A1) is first polymerized by a bulk method or a gas phase method using a continuous method, followed by a low crystalline or amorphous propylene-ethylene random copolymer elastomer. It is most desirable to polymerize component (A2) by a gas phase method.

(2-3) Other Polymerization Conditions The polymerization temperature can be used without any particular problem as long as it is within a commonly used temperature range. Specifically, a range of 0 ° C. to 200 ° C., more preferably 40 ° C. to 100 ° C. can be used.
Although the polymerization pressure varies depending on the process to be selected, it can be used without any problem as long as it is in a pressure range usually used. Specifically, a range of greater than 0 to 200 MPa, more preferably 0.1 MPa to 50 MPa can be used. At this time, an inert gas such as nitrogen can be coexisted.
In the case where the sequential polymerization of the component (A1) in the first step and the component (A2) in the second step is performed, it is desirable to add a polymerization inhibitor into the system in the second step. When producing a propylene-ethylene block copolymer, a polymerization inhibitor is added to a reactor that performs ethylene-propylene random copolymerization in the second step. Product quality can be improved. Various technical studies have been made on this technique, and examples thereof include Japanese Patent Publication Nos. 63-54296, 7-25960, and 2003-2939. It is desirable to apply the method to the present invention.

3. Method for controlling constituent elements of propylene-ethylene block copolymer Each element of the propylene-ethylene block copolymer (A) used in the polypropylene film of the present invention is controlled as follows, and the propylene-ethylene block of the present invention is controlled as follows. It can manufacture so that the structural requirements required for a copolymer (A) may be satisfy | filled.

(1) About component (A1) About crystalline propylene-ethylene random copolymer component (A1), it is necessary to control ethylene content E (A1) and T (A1).
In the present invention, in order to control E (A1) within a predetermined range, the amount ratio of propylene and ethylene supplied to the polymerization tank in the first step may be appropriately adjusted. The relationship between the supply ratio and the ethylene content in the resulting propylene-ethylene random copolymer varies depending on the type of metallocene catalyst used, but the component (A1) having the ethylene content E (A1) required by adjusting the supply ratio is added. Can be manufactured. For example, when E (A1) is controlled to 0 to 7 wt%, the supply weight ratio of ethylene to propylene may be in the range of 0 to 0.3, preferably in the range of 0 to 0.2. At this time, the component (A1) has a narrow crystallinity distribution, and T (A1) decreases as E (A1) increases.
Therefore, in order for T (A1) to satisfy the scope of the present invention, E (A1) and the relationship between these are grasped and adjusted to take a target range.

(2) Component (A2) Regarding the low crystalline or amorphous propylene-ethylene random copolymer component (A2), it is necessary to control the ethylene contents E (A2) and T (A2).
In the present invention, in order to control E (A2) within a predetermined range, the ratio of ethylene supply to propylene in the second step may be controlled in the same manner as E (A1). For example, when E (A2) is controlled to 5 to 20 wt%, the supply weight ratio of ethylene to propylene may be in the range of 0.01 to 5, preferably in the range of 0.05 to 2. At this time, although the crystallinity distribution of the component (A2) is slightly increased as the ethylene content is increased, T (A2) is decreased as E (A2) is increased as in the case of the component (A1).
Therefore, in order for T (A2) to satisfy the scope of the present invention, the relationship between E (A2) and T (A2) is grasped, and E (A2) is controlled to be within a predetermined range. Good.

(3) About W (A1) and W (A2) The amount W (A1) of component (A1) and the amount W (A2) of component (A2) are the production amounts of the first step for producing component (A1). It can be controlled by changing the ratio of the production amount of the component (A2). For example, in order to increase W (A1) and decrease W (A2), the production amount of the second step may be reduced while maintaining the production amount of the first step, which shortens the residence time of the second step. It can be easily controlled by lowering the polymerization temperature or increasing the amount of the polymerization inhibitor. The reverse is also true.
When actually setting the conditions, it is necessary to consider the activity decay. That is, in the range of the ethylene content E (A1) and E (A2) carried out in the present invention, generally, the polymerization activity increases when the ratio of ethylene supply to propylene is increased in order to increase the ethylene content. The activity decay tends to increase. Therefore, in order to maintain the activity of the second step, it is necessary to suppress the polymerization activity of the first step. Specifically, the production amount W (A1) is lowered in the first step, and the polymerization is performed as necessary. Lower the temperature and / or shorten the polymerization time (residence time), or increase the ethylene content E (A2) in the second step, increase the production W (A2), and raise the polymerization temperature as necessary And / or conditions may be set in such a way as to increase the polymerization time (residence time).

(4) Glass transition temperature Tg In the propylene-ethylene block copolymer used in the present invention, the glass transition temperature Tg described in paragraph 0025 needs to have a single peak. In order for Tg to have a single peak, the difference [E] gap or E (A2) between the ethylene content E (A1) in component (A1) and the ethylene content E (A2) in component (A2) ) -E (A1) may be 20 wt% or less, preferably 18 wt%, more preferably 16 wt% or less, and E (gap) may be reduced to a range where Tg becomes a single peak in actual measurement.
Depending on the ethylene content E (A1) of the crystalline copolymer component (A1), the ethylene content E (A2) of the low crystalline or non-crystalline copolymer component (A2) is within an appropriate range. By setting the supply weight ratio of ethylene to propylene during the polymerization of component (A2), it is possible to obtain a polymer having a predetermined [E] gap.
The Tg of the block copolymer that does not take a phase separation structure as in the present invention is the ethylene content E (A1) in the component (A1), the ethylene content E (A2) in the component (A2), and It is affected by the ratio of both components. In the present invention, the amount of the component (A2) is 5 to 70 wt%, but in this range, Tg is more strongly affected by the ethylene content E (A2) in the component (A2).
That is, Tg reflects the glass transition of the amorphous part, whereas in the block copolymer component (A) of the present invention, the component (A1) has crystallinity and relatively few amorphous parts, This is because the component (A2) is low crystalline or amorphous and most of it is an amorphous part.
Therefore, the value of Tg is controlled approximately by E (A2), and the control method of E (A2) is as described above in paragraph 0057.

(5) Melt flow rate (MFR) In the propylene-ethylene block copolymer (A) of the present invention, a crystalline copolymer component (A1) and a low crystalline or amorphous material are used to maintain transparency. Since it is essential that the copolymer elastomer component (A2) is compatible, the viscosity [η] A1 of the component (A1), the viscosity [η] A2 of the component (A2), propylene-ethylene block copolymer An apparent viscosity mixing rule is generally established between the total viscosity [η] W of the combined (A). That is,
Log [η] W = {W (A1) × Log [η] A1 + W (A2) × Log [η] A2} / 100
Is generally established. In general, there is a certain correlation between MFR and [η], so from the viewpoint of flexibility and heat resistance, [η] A2, W (A1), and W (A2) are set first. The MFR can be freely controlled by changing [η] A1 according to the above equation.

(6) About T (A4) T (A4) is an index indicating the crystallinity distribution, and the narrower the crystallinity distribution of the component (A1) is, the closer T (A4) is to T (A1) (lower ), Controlling T (A4) to be low is nothing other than controlling the crystallinity distribution of component (A1) and component (A2) narrowly.
In general, by using a metallocene catalyst, a polymer having a narrower crystallinity distribution can be obtained than when using a Ziegler-Natta catalyst. It is not necessary and sufficient to use a metallocene catalyst in order to narrow the sex distribution.
In order to adjust the final propylene-ethylene block copolymer to those having desirable physical properties, the component (A1) and the component (A2) need to have different specific polymer compositions. That is, in the first step and the second step, it is necessary to keep the polymerization conditions corresponding to the respective polymer compositions, particularly the monomer gas composition, at different specific values. Therefore, when the crystallinity distribution of the component (A2) is wide in the adopted process, the transfer step is adjusted so that the specific monomer gas mixture corresponding to the first step is not brought into the second step from the first step. It is necessary to devise such as. Specifically, the crystallinity distribution of the component (A2) can be narrowed by increasing the purge amount in the transfer step, or by diluting or substituting with an inert gas such as nitrogen. That is, T (A4) can be controlled to be low by adjusting the transfer process.

(7) About W (Mw ≦ 5,000) In general, a polymer having a narrower molecular weight distribution than that of a Ziegler-Natta catalyst can be obtained by using a metallocene catalyst. However, in a system that performs sequential polymerization as in the present invention, it is not always sufficient to use a metallocene catalyst in order to narrow the molecular weight distribution. In particular, in order to prevent the formation of low molecular weight components, the time for transferring from the first step to the second step can be shortened, or the monomer gas mixture corresponding to the first step in the transfer step can be replaced with an inert gas such as nitrogen. By completely substituting, W (Mw ≦ 5,000) can be controlled to be small independently of the polymerization conditions.

4). Additional ingredients (additives)
An ethylene-α-olefin copolymer component may be blended with the polypropylene heat-shrinkable film of the present invention for the purpose of improving heat shrinkability and impact resistance. The standard of the blending amount is approximately 0 to 10 wt%, and if it exceeds 10 wt%, the transparency is likely to deteriorate.

The ethylene-α-olefin copolymer is a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms, and preferably has an ethylene content of 95 to 60 wt%. When the ethylene content exceeds 95 wt%, the effects of improving heat shrinkability and impact resistance are not easily observed, and when the ethylene content is less than 60 wt%, the transparency tends to deteriorate.
Moreover, it is preferable that the density of this ethylene-alpha-olefin copolymer is 0.870-0.920 g / cm < ³ >. When the density is less than 0.870 g / cm ³ , stickiness tends to occur and the blocking resistance deteriorates. When the density exceeds 0.920 g / cm ³ , the effects of improving heat shrinkability and impact resistance are not easily observed.

In addition, the resin composition for polypropylene heat-shrinkable film of the present invention has a fat such as petroleum resin, terpene resin, rosin resin, coumarone indene resin, and hydrogenated derivatives thereof for the purpose of improving heat shrinkability. A cyclic hydrocarbon resin, an amorphous cyclic olefin resin, or the like may be added.
As the alicyclic hydrocarbon resin, a resin having no polar group or a resin having a hydrogenation rate of 95% or more by adding hydrogen is preferable. A more preferable resin is petroleum resin or a hydrogenated derivative of petroleum resin, and examples of the petroleum resin include commercially available products such as Alcon manufactured by Arakawa Chemical Industries, Ltd. or Opera manufactured by ExxonMobil Co., Ltd. .
Non-crystalline cyclic olefin-based resins include polymers such as cyclopentadiene and tetracyclododecene, and copolymers mainly composed of them, and commercially available products include Apel manufactured by Mitsui Chemicals and ZEONOR manufactured by Nippon Zeon. Etc. can be exemplified.
The standard of the amount is generally less than 5 w%. If it is 5% by weight or more, the polypropylene heat-shrinkable film made of the resin composition of the present invention tends to be brittle.
The alicyclic hydrocarbon resin and the amorphous cyclic olefin resin are those having a softening point temperature of 110 ° C. or higher and 160 ° C. or lower, or a glass transition temperature of 50 ° C. or higher and 120 ° C. or lower. From the viewpoint of

  In the polypropylene heat-shrinkable film of the present invention, a nucleating agent, an antioxidant, a neutralizing agent, a light stabilizer, an ultraviolet absorber, which are used as a known compounding agent for polyolefin resin as long as the effects of the present invention are not impaired. Various additives such as an antiblocking agent, a lubricant, an antistatic agent, a metal deactivator, a peroxide, a filler, an antibacterial antifungal agent, and a fluorescent brightening agent may be blended. The amount of these additives is generally 0.0001 to 3% by weight, preferably 0.001 to 1% by weight.

5. Polypropylene heat-shrinkable film (1) Production method of film The polypropylene-based heat-shrinkable film of the present invention is obtained by stretching an unstretched sheet containing at least one layer of the propylene-ethylene block copolymer in at least a uniaxial direction, and preferably It is obtained by aging and controlling the shrinkage with time.

(2) Manufacture of an unstretched sheet A well-known film or sheet forming method can be used for manufacture of an unstretched sheet. As a specific example, a raw material is plasticized by an extruder, and a resin is melt-extruded from a T-die and is cast and solidified using an air knife and a cooling roll. Examples thereof include sheet molding and inflation molding in which a resin melt-extruded from an annular die is cooled and solidified by air cooling or water cooling.

(3) Stretching method As the stretching method, a known method can be used, and examples thereof include a tubular method, a tenter-type stretching method, a roll stretching method using a speed difference between rolls, and a pantograph batch stretching method. .
An example of the stretching method is a method in which a sheet obtained by a T-die method is roll-stretched by about 1.0 to 5.0 times, and then stretched by about 4.0 to 10.0 times by a tenter method.
As another example of the stretching method, a tube-shaped unstretched sheet obtained from an annular die by air cooling or water cooling is heated to a melting temperature or lower, and then in a bubble direction by air in the longitudinal direction of 3.0 to 7 Examples of the stretching method include a so-called tubular method that stretches about 3.0 times to about 7.0 times in the lateral direction.
For the purpose of improving the shrinkage rate, the stretching is preferably performed at a low temperature as much as possible without causing stretch cracks. Particularly, when there is a step of preheating the unstretched sheet, the preheating temperature can be molded. Among these, it is preferable to make it as low as possible from the viewpoint of improving shrinkage.

Since the propylene-ethylene block copolymer used in the present invention is produced using a metallocene catalyst, the crystallinity distribution toward the high crystalline component side is narrow. It is difficult to occur. Therefore, the stretched film in the present invention is preferably molded in terms of quality at a stretching temperature that is 20 ° C. or lower than the melting point of the block copolymer.
After stretching, a known heat treatment such as so-called aging is preferably performed in order to suppress the shrinkage with time. Conditions for heat treatment such as aging can be appropriately set in view of the balance between shrinkage with time and heat shrinkage.
In addition, the lamination method when the polypropylene heat-shrinkable film of the present invention is a multilayer film includes a multilayer coextrusion method and an inline lamination method, but the multilayer coextrusion method is preferable from the viewpoint of simplifying manufacturing equipment.

In the following, in order to more specifically and clearly describe the present invention, the present invention will be described in contrast to examples and comparative examples to demonstrate the rationality and significance of the requirements of the configuration of the present invention.
The evaluation methods and resins used in the examples and comparative examples are as follows.

[Method for measuring physical properties of propylene-ethylene block copolymer (A)]
1) Melt flow rate (MFR)
According to JIS K7210 A method condition M, it measured on condition of the following.
Test temperature: 230 ° C
Nominal weight: 2.16kg
Die shape: Diameter 2.095mm Length 8.00mm

2) TREF
A sample is dissolved in o-dichlorobenzene (containing 0.5 mg / ml BHT) at 140 ° C. to prepare 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. Thereafter, o-dichlorobenzene (containing 0.5 mg / ml BHT) as a solvent is caused to flow through the column at a flow rate of 1 ml / min, and components dissolved in o-dichlorobenzene at −15 ° C. in the TREF column. Elution is performed for 10 minutes, and then the column is linearly heated to 140 ° C. at a heating rate of 100 ° C./hour to obtain an elution curve.
〔apparatus〕
(TREF part)
TREF column: 4.3 mmφ × 150 mm stainless steel column Column packing material: 100 μm surface inert treatment glass beads Heating method: Aluminum heat block Cooling method: Peltier element (Peltier element is cooled by water)
Temperature distribution: ± 0.5 ° C
Temperature controller: Chino Corporation Digital Program Controller KP1000 (Valve Oven)
Heating method: Air bath oven Measurement temperature: 140 ° C
Temperature distribution: ± 1 ° C
Valve: 6-way valve 4-way valve (sample injection part)
Injection method: Loop injection method Injection volume: Loop size 0.1ml
Inlet heating method: Aluminum heat block measurement temperature: 140 ° C
(Detection unit)
Detector: Fixed wavelength infrared detector FOXBORO MIRAN 1A
Detection wavelength: 3.42 μm
High-temperature flow cell: Micro flow cell for LC-IR Optical path length: 1.5 mm Window shape: 2φ x 4 mm long circle Synthetic sapphire window measurement temperature: 140 ° C
(Pump part)
Liquid feed pump: SSC-3461 pump manufactured by Senshu Kagaku Co. [Measurement conditions]
Solvent: o-dichlorobenzene (containing 0.5 mg / ml BHT)
Sample concentration: 5 mg / ml
Sample injection volume: 0.1 ml
Solvent flow rate: 1 ml / min

3) Measurement of solid viscoelasticity A sample cut into a strip of 10 mm width × 18 mm length × 2 mm thickness from a 2 mm thick sheet injection-molded under the following conditions was used. The apparatus used was ARES manufactured by Rheometric Scientific. The frequency is 1 Hz. The measurement temperature was raised stepwise from −60 ° C., and the measurement was performed until the sample melted and became impossible to measure. The strain was performed in the range of 0.1 to 0.5%.
[Preparation of specimen]
Standard number: JIS-7152 (ISO294-1)
Molding machine: TU-15 injection molding machine manufactured by Toyo Machine Metal Co., Ltd. Setting temperature: 80, 80, 160, 200, 200.200 ° C. from below the hopper
Mold temperature: 40 ℃
Injection speed: 200 mm / sec (speed in the mold cavity)
Injection pressure: 800 kgf / cm ²
Holding pressure: 800 kgf / cm ²
Holding time: 40 seconds Mold shape: Flat plate (thickness 2 mm, width 30 mm, length 90 mm)

4) DSC
Using a Seiko DSC, take 5.0 mg of sample, hold at 200 ° C. for 5 minutes, crystallize to 40 ° C. at a rate of temperature decrease of 10 ° C./min, and further melt at a rate of temperature increase of 10 ° C./min. The melting peak temperature was Tm (unit: ° C.). DHm was determined from the area of the endothermic curve at the time of temperature increase.

5) GPC
The weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured by gel permeation chromatography (GPC).
Conversion from the retention volume to the molecular weight is performed using a calibration curve prepared in advance with standard polystyrene. The measurement method is the method detailed in paragraph 0038.

6) Calculation of ethylene content According to the method described in detail in paragraphs 0029 to 0033.

7) The heat resistance of the block copolymer (A) was evaluated under the following conditions using the test piece used for the measurement of heat resistant solid viscoelasticity.
Standard number: JIS K7206 (Conforms to the 50 method except that the load is 250 g)
Measuring machine: Fully automatic HDT measuring machine (manufactured by Toyo Seiki)
Shape of the test piece: 2 mm thick 25 mm × 25 mm Two flat plates are prepared. Test piece preparation method: Injection molded flat plate is punched into the shape described above. Leave as it is (no annealing)
Test weight: 250g
Temperature increase rate: 50 ° C./hour Number of test pieces: 3

[Production Example PP-1]
[Polymerization Production Example A-1]
Preparation of prepolymerization catalyst (chemical treatment of ion-exchange layered silicate) In a glass separable flask equipped with a 10-liter stirring blade, 3.75 liters of distilled water, followed by 2.5 kg of concentrated sulfuric acid (96%) Slowly added. At 50 ° C., 1 kg of montmorillonite (Menzawa Chemical Co., Ltd. Benclay SL; average particle size = 25 μm, particle size distribution = 10-60 μm) was 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 weight after drying was 707 g.
(Drying of ion-exchanged layered silicate) The silicate previously chemically treated was dried by a kiln dryer. Specifications and drying conditions are as follows.
Rotating cylinder: Cylindrical inner diameter 50 mm Heating zone 550 mm (Electric furnace) Speed with rotating blade: 2 rpm Tilt angle: 20/520 Silicate feed rate: 2.5 g / min Gas flow rate: Nitrogen 96 liters / hour Countercurrent drying Temperature: 200 ° C (powder temperature)
(Preparation of catalyst) An autoclave having an internal volume of 16 liters having a stirring and temperature control device was sufficiently replaced with nitrogen. 200 g of the silicate was introduced, 1,160 ml of mixed heptane and 840 ml of a heptane solution of triethylaluminum (0.60 M) were added and stirred at room temperature. After 1 hour, the mixture was washed with mixed heptane to prepare 2,000 ml of silicate slurry. Next, 9.6 ml of a heptane solution of triisobutylaluminum (0.71 ML) was added to the silicate slurry prepared above and reacted at 25 ° C. for 1 hour. In parallel, with 2.180 mg (0.3 mM) of (r) -dichloro [1.1'-dimethylsilylenebis [2-methyl-4- (4-chlorophenyl) -4H-azulenyl}] zirconium mixed in 870 ml of heptane. Then, 33.1 ml of a heptane solution of triisobutylaluminum (0.71 M) was added, and the mixture reacted at room temperature for 1 hour was added to the silicate slurry. After stirring for 1 hour, 5,000 ml was added with mixed heptane. Prepared.
(Preliminary polymerization / washing) Subsequently, the temperature in the tank was raised by 40 ° C., and when the temperature was stabilized, 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, the stirring was stopped and the mixture was allowed to stand for about 10 minutes, and then the supernatant was decanted to 2,400 ml. Subsequently, 9.5 ml of a heptane solution of triisobutylaluminum (0.71 ML) and 5600 ml of mixed heptane were further added, stirred at 40 ° C. for 30 minutes, allowed to stand for 10 minutes, and then 5600 ml of the supernatant was removed. 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 / liter, the Zr concentration was 8.6 × 10 −6 g / L, and the abundance in the supernatant relative to the charged amount was It was 0.016%. Subsequently, 170 ml of a heptane solution of triisobutylaluminum (0.71 ML) was added, followed by drying at 45 ° C. under reduced pressure. A prepolymerized catalyst containing 2.0 g of polypropylene per 1 g of catalyst was obtained.

First Step In the first step, propylene-ethylene random copolymerization was carried out using a liquid phase polymerization tank equipped with a stirrer having an internal volume of 0.4 m ³ . Liquefied propylene, liquefied ethylene, and triisobutylaluminum were continuously fed at 90 kg / hour, 4.2 kg / hour, and 21.2 g / hour, respectively. The hydrogen supply amount was adjusted so that the MFR in the first step became a target value. Further, the above prepolymerized catalyst was supplied as a catalyst (excluding the weight of the prepolymerized polymer) so as to be 6.9 g / hour. The polymerization tank was cooled so that the polymerization temperature was 45 ° C.
Analysis of the propylene-ethylene random copolymer obtained in the first step revealed that the BD (bulk density) was 0.46 g / cc, the MFR was 2.0 g / 10 min, and the ethylene content was 3.7 wt%. .

Second Step In the second step, propylene-ethylene random copolymerization was carried out using a stirred gas phase polymerization tank having an internal volume of 0.5 m ³ . The slurry containing polymer particles was continuously withdrawn from the liquid phase polymerization tank in the first step, flushed with liquefied propylene, and then pressurized with nitrogen and continuously supplied to the gas phase polymerization tank.
The polymerization tank was controlled so that the temperature was 80 ° C. and the total partial pressure of propylene, ethylene, and hydrogen was 1.5 MPa. At that time, the concentration of propylene, ethylene and hydrogen in the total partial pressure of propylene, ethylene and hydrogen was controlled to be 66.97 vol%, 32.99 vol% and 420 volppm, respectively.
Furthermore, ethanol was supplied to the gas phase polymerization tank as an activity inhibitor. The supply amount of ethanol was set to 0.3 mol / mol with respect to aluminum in TIBA supplied along with the polymer particles supplied to the gas phase polymerization tank.
When the propylene-ethylene block copolymer thus obtained was analyzed, the activity was 8.7 kg / g-catalyst, the BD was 0.41 g / cc, the MFR was 2.0 g / 10 min, and the ethylene content was 8.7 wt. %Met.

(Granulation)
An antioxidant, a neutralizing agent, an antiblocking agent, and a lubricant were added to the block copolymer powder obtained in Polymerization Production Example A-1 by a blender, and the mixture was sufficiently stirred and mixed.
Antioxidant: Tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane (manufactured by Ciba Specialty Chemicals, Inc., Irganox 1010) 0.05 Parts by weight, tris (2,4-di-t-butylphenyl) phosphite (manufactured by Ciba Specialty Chemicals Co., Ltd. Irgafos 168) 0.10 parts by weight neutralizing agent: calcium stearate (manufactured by NOF Corporation Stearate G) 0.05 part by weight Antiblocking agent: Synthetic silica (Silicia 430 manufactured by Fuji Silysia Co., Ltd.) 0.40 part by weight Lubricant: Oleic acid amide (Neontron manufactured by Nippon Seika Co., Ltd.) 0.30 weight Part

  The copolymer powder to which the additive was added was mixed at 750 rpm with a Henschel mixer at room temperature for 1 minute at room temperature, and then a PCM twin screw extruder manufactured by Ikegai Seisakusho with a screw diameter of 30 mm, screw rotation speed 200 rpm, discharge rate 10 kg / hr, The melted resin is melt kneaded at an extruder temperature of 190 ° C., the molten resin extruded from the strand die is taken out while being cooled and solidified in a cooling water tank, and the strand is cut into a length of about 3 mm and a diameter of about 2 mm using a strand cutter. -The raw material pellet (PP-1) of the ethylene block copolymer (A) was obtained.

(analysis)
Using the obtained PP-1 pellets, TREF, ethylene content, DSC, GPC, solid viscoelasticity, and heat resistance were measured.
Table 4 shows each data obtained by the measurement.
From the measurement results obtained, it can be said that PP-1 satisfies all the requirements as component (A).
Here, in order to show the position of each parameter in the TREF measurement result, an elution curve is illustrated in FIG. In order to show the position of each parameter in the solid viscoelasticity measurement results, FIG. 2 illustrates changes in storage elastic modulus G ′, loss elastic modulus G ″ and loss tangent tan δ with respect to temperature.

[Production Example PP-1B]
[Production Examples PP-2 to 3]
[Polymerization Production Examples A-2 to 3]
In the same manner as in Polymerization Production Example A-1, the polymerization conditions were changed to produce a propylene-ethylene block copolymer. The polymerization conditions and polymerization results are shown in Table 3.
Using the obtained polymer powder, PP-2 to 3 were obtained by the same additive formulation and granulation conditions as in Production Example PP-1. Various analysis results are shown in Table 4.

[Production Example PP-4]
[Polymerization Production Example A-4]
In Polymerization Production Example A-1, polymerization was carried out in the same manner as in Polymerization Production Example A-1, except that only the first step was carried out without carrying out the second step, to produce a propylene-ethylene random copolymer. went. The polymerization conditions and polymerization results are shown in Table 3.
Using the obtained polymer powder, PP-4 was obtained by the same additive formulation and granulation conditions as in Production Example PP-1. Various analysis results are shown in Table 4.

[Production Example PP-5]
[Polymerization Production Example A-5]
(Preparation of solid catalyst component)
2,000 milliliters of dehydrated and deoxygenated n-heptane was introduced into a flask thoroughly purged with nitrogen, and then 2.6 mol of MgCl ₂ and 5.2 mol of Ti (On-C ₄ H ₉ ) ₄ were introduced. The mixture was introduced and reacted at 95 ° C. for 2 hours. After completion of the reaction, the temperature was lowered to 40 ° C., and then 320 ml of methylhydropolysiloxane (20 centistokes) was introduced and reacted for 3 hours. The resulting solid component was washed with n-heptane.
Next, 4,000 milliliters of n-heptane purified in the same manner as described above was introduced into a sufficiently nitrogen-substituted flask, and 1.46 mol of the solid component synthesized above was introduced in terms of Mg atoms. Next, 25 ml of n-heptane was mixed with 2.62 mol of SiCl ₄ , introduced into the flask at 30 ° C. for 30 minutes, and reacted at 70 ° C. for 3 hours. After completion of the reaction, washing with n-heptane was performed. Next, 0.15 mol of phthalic acid chloride was mixed with 25 ml of n-heptane, introduced into the flask at 70 ° C. for 30 minutes, and reacted at 90 ° C. for 1 hour. After completion of the reaction, washing with n-heptane was performed. Next, 11.4 mol of TiCl ₄ was introduced and reacted at 110 ° C. for 3 hours. After completion of the reaction, the solid component (A1) was obtained by washing with n-heptane. The titanium content of this solid component was 2.0 wt%.
Next, the autoclave having an internal volume of 16 liters having a stirring and temperature control device was sufficiently replaced with nitrogen, and 5,000 milliliters of n-heptane purified in the same manner as above was introduced into the solid component (A1 ) Was introduced, and 0.875 mol of SiCl ₄ was introduced and reacted at 90 ° C. for 2 hours. After completion of the reaction, further (CH ₂ ═CH) Si (CH ₃ ) ₃ 0.15 mol, (t-C ₄ H ₉ ) (CH ₃ ) Si (OCH ₃ ) ₂ 0.075 mol and Al (C ₂ H ₅ ) ₃ 0.4 mol was sequentially introduced and contacted at 30 ° C. for 2 hours. After completion of the contact, the solid catalyst component (A) mainly composed of magnesium chloride was obtained by thoroughly washing with n-heptane. The titanium content of this product was 1.8 wt%.
(Preliminary polymerization)
An autoclave with an internal volume of 16 liters equipped with a stirring and temperature control device was sufficiently replaced with nitrogen. Here, 100 g of the n-heptane slurry of the solid catalyst component (A) prepared above was introduced as the solid catalyst component (A), and n-heptane was further introduced to adjust the liquid level to 5000 ml. Next, the temperature in the tank was adjusted to 15 ° C., and 0.1 mol of triethylaluminum / n-heptane solution (10 wt%) was added as Al (C ₂ H ₅ ) ₃ . Thereafter, prepolymerization was performed by supplying propylene at a rate of 50 g / hour for 2 hours. After completion of the prepolymerization, the residual monomer was purged and the solid catalyst was thoroughly washed with n-heptane. After the washing, drying under reduced pressure was performed to obtain a prepolymerized catalyst. The prepolymerized catalyst contained 2.0 g of polypropylene per 1 g of the solid catalyst component.
Polymerization Production Example A-1 except that the prepolymerization catalyst thus obtained was used, and triethylaluminum was continuously fed at 10 g / hour instead of triisobutylaluminum, and the polymerization conditions shown in Table 3 were used. Propylene-ethylene block copolymer was produced in the same manner as described above. The polymerization results are shown in Table 3.
Using the obtained polymer powder, PP-5 was obtained by the same additive formulation and granulation conditions as in Production Example PP-1. Various analysis results are shown in Table 4.

[Example 1]
Using the obtained PP-1 pellet as a raw material, a polypropylene heat-shrinkable film was molded under the following conditions.
[Production of heat-shrinkable film]
(1) Molding method of unstretched sheet PP-1 is melt-extruded from a T-die at a molding temperature of 220 ° C using a single screw extruder, and cooled and solidified with a cooling roll at 15 ° C to form an unstretched sheet having a thickness of 400 microns. Obtained.
(2) Forming method of stretched film The unstretched sheet is introduced into a tenter furnace, preheated at 100 ° C. for 30 seconds, and stretched 6.5 times over 30 seconds in the width direction in a temperature atmosphere equivalent to the preheating temperature. Subsequently, annealing was performed at 85 ° C. for 30 seconds while relaxing by 7.5% in the width direction in the same tenter furnace. A heat-shrinkable film having a draw ratio of 6 times and a thickness of 60 μm was obtained. The obtained heat-shrinkable film was conditioned at 40 ° C. for 1 day to obtain a sample for evaluation.

[Evaluation of film properties]
1) Heat shrinkage ratio: cut into a square shape of 10 cm × 10 cm so that one side thereof is parallel to the flow direction of the film, and this is cut at a predetermined temperature (80 ° C., 90 ° C., 100 ° C., 110 ° C., 120 ° C. And immersed in an oil bath heated to 140 ° C. for 10 seconds. Immediately after 10 seconds, the film was immersed in a separately prepared 25 ° C. oil bath for 20 seconds, and then the length in the direction perpendicular to the film flow direction was measured.
2) Haze (unit:%): The transparency of the obtained stretched film was evaluated by haze measurement. The measuring method was based on JIS K7136-2000.
3) Tensile modulus (unit: Mpa): Measured for each of the film flow direction (MD) and the orthogonal direction (TD) under the following conditions, and used as a measure of film rigidity. The calculation method of the tensile elastic modulus conformed to JIS K-7127-1999.
Sample length: 150mm
Sample width: 15mm
Distance between chucks: 100mm
Crosshead speed: 1mm / min
4) Flexibility after shrinkage: The tensile elastic modulus of the film after shrinkage used in the measurement of the heat shrinkage rate (120 ° C) of 1) was measured according to JIS K-7127-1999 in the same manner as 3).
5) Blocking property About 50 sheets of the obtained heat-shrinkable film were stacked and evaluated after being allowed to stand for 1 month in an environment of 23 ° C. and 50% humidity. The case where blocking was not generated or very slight was marked with ◯, and the case where blocking was clearly generated was marked with X.

[Example 2]
A polypropylene heat-shrinkable film was obtained in the same manner as in Example 1 except that PP-1 in Example 1 was replaced with PP-2. Table 5 shows the evaluation results of the obtained heat-shrinkable film.
[Comparative Example 1]
A polypropylene heat-shrinkable film was obtained in the same manner as in Example 1 except that PP-1 in Example 1 was replaced with PP-3. Table 5 shows the evaluation results of the obtained heat-shrinkable film. Since there were a plurality of tan δ peaks, the transparency was poor.
[Comparative Example 2]
A polypropylene heat-shrinkable film was obtained in the same manner as in Example 1 except that PP-1 in Example 1 was replaced with PP-4. Table 5 shows the evaluation results of the obtained heat-shrinkable film. Since it was not a block copolymer but a random copolymer, it was inferior in flexibility as compared with the Examples, and was inferior in heat shrinkage.
[Comparative Example 3]
A polypropylene heat-shrinkable film was obtained in the same manner as in Example 1 except that PP-1 in Example 1 was replaced with PP-5. Table 5 shows the evaluation results of the obtained heat-shrinkable film. Since it was not polymerized by a metallocene catalyst, stickiness was conspicuous and blocking occurred. Moreover, the heat shrinkage rate was inferior.

[Consideration by contrast between Example and Comparative Example]
Considering each of the above Examples and Comparative Examples in contrast, the provision of the present invention is achieved using the novel propylene-ethylene block copolymer composition of the present invention that satisfies the respective provisions of the constitution of the present invention. The heat-shrinkable film molded according to the molding conditions to be satisfied is very excellent in transparency and flexibility, and there is no blocking property of the product. It is understood that it is confirmed.
In Comparative Example-1, since the tan δ peak of the block copolymer (A) is not single, the phase separation structure is taken and the transparency is deteriorated.
In comparative example-2, the case where the random copolymer by a metallocene catalyst was used instead of a block copolymer was shown. Although there was no problem with blocking resistance, it was inferior in flexibility because it was not a block copolymer.
In Comparative Example-3, since the block copolymer (A) was not polymerized with a metallocene catalyst, the blocking resistance was deteriorated.
As described above, compared with the heat-shrinkable film of the propylene-ethylene block copolymer of the present invention, which has excellent properties such as transparency, flexibility, and heat shrinkability, and less blocking, each comparative example has a quality However, the characteristics of the polypropylene heat-shrinkable film of the present invention are emphasized.

It is a graph which shows the elution amount curve and elution amount integration of PP-1. It is a graph which shows the solid viscoelasticity measurement of PP-1. It is a graph which shows the solid viscoelasticity measurement of PP-3.

Claims (8)

A polypropylene-based heat-shrinkable film imparted with heat-shrinkability by stretching in at least one direction using a propylene-ethylene block copolymer satisfying the following conditions (Ai) to (A-iii) as a raw material.
( Ai ) 30 to 85 wt% of propylene-ethylene random copolymer component (A1) having propylene alone or ethylene content of 7 wt% or less in the first step using the metallocene catalyst, and component (A1) in the second step A propylene-ethylene block copolymer obtained by sequential polymerization of 70 to 15 wt% of a propylene-ethylene random copolymer component (A2) containing 3 to 20 wt% more ethylene than (A-ii) ) Melt flow rate (MFR: 2.16 kg 230 ° C.) is in the range of 0.1-30 g / 10 min (A-iii) Temperature-loss tangent (tan δ) curve obtained by solid viscoelasticity measurement (DMA) The tan δ curve has a single peak below 0 ° C It includes at least one layer using a propylene-ethylene block copolymer (A) satisfying the following conditions (Ai) to (A-iii) as a raw material, and has heat shrinkability by stretching in at least one direction. Multilayer polypropylene heat-shrinkable film applied.
( Ai ) 30 to 85 wt% of propylene-ethylene random copolymer component (A1) having propylene alone or ethylene content of 7 wt% or less in the first step using the metallocene catalyst, and component (A1) in the second step A propylene-ethylene block copolymer obtained by sequential polymerization of 70 to 15 wt% of a propylene-ethylene random copolymer component (A2) containing 3 to 20 wt% more ethylene than (A-ii) ) Melt flow rate (MFR: 2.16 kg 230 ° C.) is in the range of 0.1-30 g / 10 min (A-iii) Temperature-loss tangent (tan δ) curve obtained by solid viscoelasticity measurement (DMA) The tan δ curve has a single peak below 0 ° C The polypropylene-based heat-shrinkable film according to claim 1 or 2, wherein the stretching is performed at a temperature 20 ° C or more lower than the melting peak temperature measured by DSC of the propylene-ethylene block copolymer (A). A polypropylene-based heat-shrinkable film. A polypropylene heat-shrinkable film, wherein the polypropylene heat-shrinkable film made of the propylene-ethylene block copolymer according to any one of claims 1 to 3 is stretched and formed uniaxially by a tenter method. A polypropylene heat-shrinkable film, wherein the polypropylene heat-shrinkable film made of the propylene-ethylene block copolymer according to any one of claims 1 to 4 is biaxially stretched by an inflation method. The polypropylene-based heat-shrinkable film according to any one of claims 1 to 5, wherein the propylene-ethylene block copolymer satisfies the following condition (A-iv).
(A-iv) A component amount W (Mw ≦ 5.000) of 5,000 or less in the molecular weight of the block copolymer obtained by gel permeation chromatography (GPC) measurement is 0.000 in the component (A). 6wt% or less The polypropylene-based heat-shrinkable film according to any one of claims 1 to 6, wherein the propylene-ethylene block copolymer satisfies the following conditions (Av) to (A-vi): .
(Av) The component (A1) obtained in the first step is a propylene-ethylene random copolymer having an ethylene content in the range of 0.5 to 6 wt%, and the ratio in the whole is in the range of 30 to 85 wt%. Yes, the component (A2) obtained in the second step is a propylene-ethylene random copolymer containing 6 to 18 wt% more ethylene than (A1), and the total proportion is in the range of 70 to 15 wt% (A-vi) TREF obtained as a plot of elution amount (dWt% / dT) against temperature by temperature-elevated elution fractionation method (TREF) in the temperature range of −15 ° C. to 140 ° C. using o-dichlorobenzene solvent In the elution curve, the peak T (A1) observed on the high temperature side is in the range of 55 ° C. to 96 ° C., and the peak T (A2) observed on the low temperature side is below 45 ° C. The temperature T of 99 wt% ethylene block copolymer is eluted (A4) is 98 ° C. or less - have not observed a peak T (A2) is, the total of propylene The polypropylene heat according to any one of claims 1 to 7, wherein the propylene-ethylene block copolymer (A) satisfies the following conditions (A-vii) to (A-iii): Shrink film.
(A-vii) The component (A1) obtained in the first step is a propylene-ethylene random copolymer having an ethylene content in the range of 1.5 to 6 wt%, and the ratio in the whole is in the range of 30 to 70 wt%. Yes, the component (A2) obtained in the second step is a propylene-ethylene random copolymer containing 8 to 16 wt% more ethylene than (A1), and the ratio in the whole is in the range of 70 to 30 wt% .
(A-ix) TREF obtained as a plot of elution amount (dWt% / dT) against temperature by the temperature rising elution fractionation method (TREF) in the temperature range of -15 ° C to 140 ° C using o-dichlorobenzene solvent In the elution curve, the peak T (A1) observed on the high temperature side is in the range of 60 ° C. to 88 ° C., the peak T (A2) observed on the low temperature side is 40 ° C. or lower, or the peak T (A2) Is not observed, and the temperature T (A4) at which 99 wt% of the total propylene-ethylene block copolymer elutes is 90 ° C. or lower.

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