JP2009242667A - Propylene resin composition and foamed material obtained from it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foamed sheet/film having excellent transparency, well-balanced permeability and reflectivity, and a smaller foamed cell diameter. <P>SOLUTION: The propylene resin composition consists of 100-50 pts.wt. of a syndiotactic propylene polymer (A) and 0-50 pts.wt. of a propylene-α-olefin copolymer (B) provided that the total of the (A) and (B) is 100 pts.wt. The (A) is a propylene polymer comprising 90-100 mol% of a propylene unit and 0-10 mol% of one or more kinds of units selected from ethylene and a 4-20C α-olefin provided that the total of the units is 100 mol%, and satisfies the following requirements [1]-[3]: [1] a fraction (rrrr) measured by<SP>13</SP>C-NMR is ≥85%; [2] a melting point (Tm) is ≥145°C and heat of fusion (ΔH) is ≥40 mJ/mg; [3] intrinsic viscosity [η] (dL/g) at 135°C and melt tension MT (mN) at 230°C satisfy the following relational expression (Eq-1) 0.25×[η]<SP>4.8</SP>≤MT≤2.00×[η]<SP>4.8</SP>. The (B) is a propylene polymer comprising 50-100 mol% of a propylene unit and 0-50 mol% of one ore more kinds of units selected from ethylene and a 4-20C α-olefin provided that the total of the units is 100 mol%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a foam resin composition comprising a syndiotactic propylene polymer and a propylene / α-olefin copolymer, and a foam sheet or film obtained therefrom.

  Foamed sheets made of thermoplastic resins are generally lightweight, have good heat insulation and buffering properties against external stress, and are easy to thermoform, such as food containers, cushioning materials, heat insulating materials, and automotive parts. Widely used in applications. In particular, due to the recent increase in awareness of environmental impact reduction, the light weight of foam sheets has come to attract attention again.

  Among these thermoplastic resin foam sheets, foam sheets obtained from polypropylene-based resins are recognized for their excellent resin properties (heat resistance, oil resistance, etc.), and their usage is increasing in recent years. On the other hand, depending on the articles (for example, food, FDP parts, electronic parts, etc.) accommodated in the molded body, in addition to easy moldability, it is easy to transmit light, or the contained articles can be easily recognized from the outside. Transparency may be required for the molded body. Conventional polypropylene-based resin foam sheets are often inferior in transparency due to the properties of the resin itself, or for reasons such as foam cell diameter and cell dispersibility.

  In particular, a light diffusing plate that is manufactured using a resin as a main material and has light diffusibility, which is an indispensable member for FDP applications, is widely used in applications such as lighting covers, internal lighting signs, and transmissive displays. In particular, in recent years, the demand for a light diffusing plate as a surface light source body for a direct backlight of a liquid crystal display or a liquid crystal television is increasing. The light diffusing plate is required to scatter the light ray without making it travel as straight as possible and to suppress the light transmission loss due to the scattering as much as possible in order to suitably exhibit the above function. In other words, it is a required characteristic of the light diffusing plate that the light diffusing plate has both a low parallel light transmittance and a high light transmittance (total light transmittance). In order to develop such required characteristics, conventionally, a method of adding inorganic particles such as calcium carbonate, barium sulfate, and titanium oxide to a transparent resin, and partially crosslinked polymer fine particles such as styrene polymer particles are used. Although a method of scattering light by an additive by a method of adding or a method of using these in combination has been adopted, it has been said that there are many problems to be solved such as a weight problem and a cost problem.

Various light diffusion sheets, lighting fixture parts, and the like using a resin foam have been proposed for the purpose of further improving the light diffusion performance (Patent Document 1). For example, in order to improve the transparency of a foam sheet or film, a method (Patent Document 2) for controlling the number and size of foam cells in a molded body has also been proposed, but it is excellent in transparency and lightweight. It has been difficult to obtain a foamed molded product capable of lowering the density as much as contribution, that is, a highly transparent foamed sheet or film having a high foaming ratio.
Japanese Patent No. 2521388 JP 2004-99701 A

  As a result of intensive studies to develop a foam sheet or film having excellent transparency, excellent balance between transparency and reflectivity, and having a smaller foam cell diameter, the present inventors have developed a specific syndiotactic propylene polymer. The present inventors have found that a propylene-based resin composition in which a blend (A) and a specific propylene / α-olefin copolymer (B) are blended at a specific ratio can solve these problems, and has reached the present invention.

  That is, the present invention relates to syndiotactic propylene polymer (A) 100 to 50 parts by weight and propylene / α-olefin copolymer (B) 0 to 50 parts by weight [however, the sum of (A) and (B) Is 100 parts by weight), and a propylene-based resin composition.

Here, the syndiotactic propylene polymer (A) is composed of 90 to 100 mol% of structural units derived from propylene and a structural unit derived from one or more selected from ethylene and an α-olefin having 4 to 20 carbon atoms. A propylene-based polymer containing 0 to 10 mol% (however, a total of 100 mol%), which simultaneously satisfies the following requirements [1] to [3],
[1] The syndiotactic pentad fraction (rrrr) measured by ¹³ C-NMR is 85% or more.
[2] The melting point (Tm) determined by DSC is 145 ° C. or higher, and the heat of fusion (ΔH) is 40 mJ / mg or higher.
[3] The intrinsic viscosity ([η], unit dL / g) at 135 ° C. and the melt tension (MT, unit mN) at 230 ° C. satisfy the following relational expression (Eq-1).
0.25 × [η] ^4.8 ≦ MT ≦ 2.00 × [η] ^4.8 ---- (Eq-1)

The propylene / α-olefin copolymer (B) is
Propylene-based polymer containing 0 to 50 mol% of structural units derived from propylene and 50 to 100 mol% of structural units derived from ethylene and one or more α-olefins having 4 to 20 carbon atoms (however, the total 100 mol%).
The present invention relates to a foam obtained by foaming the propylene-based resin composition.
The average cell diameter of the foam is preferably 0.1 to 100 μm.
Moreover, the preferable aspect of the said foam is a foam sheet or film whose film thickness is 10-2000 micrometers.

  The present invention further relates to a method for producing a foam, characterized in that a supercritical gas is infiltrated into the propylene-based resin composition and then cooled.

  A foam sheet or film having excellent transparency, excellent balance between transparency and reflectivity, and a smaller foam cell diameter is provided.

Embodiments of the present invention will be described below.
The film of the present invention is a propylene-based film containing 90 to 100 mol% of structural units derived from propylene and 0 to 10 mol% of structural units derived from one or more selected from ethylene and an α-olefin having 4 to 20 carbon atoms. 100 mol% of a syndiotactic propylene polymer (A) which is a polymer (however, in total 100 mol%) and simultaneously satisfies the following requirements [1] to [3], and a structural unit derived from propylene: 50 mol % To 100 mol%, and a propylene-based polymer (B) containing 0 to 50 mol% of structural units derived from ethylene and one or more kinds selected from α-olefins having 4 to 20 carbon atoms (however, in total, 100 mol% ) It consists of 0 to 90 parts by weight.

  Hereinafter, films composed of the syndiotactic propylene polymer (A), the propylene / α-olefin copolymer (B), the component (A), and the component (B) will be described in order.

Syndiotactic propylene polymer (A)
The syndiotactic propylene polymer (A) according to the present invention has a constitutional unit derived from propylene from 90 mol% to 100 mol% and one or more selected from ethylene and an α-olefin having 4 to 20 carbon atoms. A propylene polymer containing 0 mol% to 10 mol% in units (however, a total of 100 mol%). As long as the syndiotactic propylene polymer (A) satisfies the above requirements [1] and [2], even if it is a homopolypropylene, an α-olefin having 2 to 20 carbon atoms (excluding propylene) ) A random copolymer or a propylene block copolymer may be used, but preferably a homopolypropylene or a propylene and an α-olefin having 2 to 20 carbon atoms (excluding propylene) random copolymer. is there.

  Here, as the α-olefin having 4 to 20 carbon atoms, 1-butene, 3-methyl-1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-octene, Examples include decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene. In addition, the syndiotactic propylene polymer (A) according to the present invention usually has a constitutional unit derived from propylene from 90 mol% to 100 mol% and an α-olefin having 2 to 20 carbon atoms (excluding propylene). It is a propylene polymer containing 0 to 10 mol% of units (provided that the total of structural units is 100 mol%), preferably 91 to 100 mol% of structural units derived from propylene and the number of carbon atoms It is a propylene polymer (provided that the total of the structural units is 100 mol%), more preferably from 0 to 9 mol% of structural units derived from 2 to 20 α-olefin (excluding propylene), more preferably The structural unit derived from propylene is 96 mol% or more and 100 mol% or less, and the carbon source A propylene polymer containing 0 to 4 mol% of structural units derived from α-olefin (excluding propylene) having 2 to 20 molecules (provided that the total of the structural units is 100 mol%).

  When the syndiotactic propylene polymer (A) according to the present invention is a propylene / α-olefin random copolymer, 94 to 99.9 mol% of structural units derived from propylene and the number of carbon atoms The structural unit derived from 2 to 20 α-olefin (excluding propylene) in an amount of 0.1 to 8 mol%, preferably 93 to 99.9 mol% of the structural unit derived from propylene, and 2 to 2 carbon atoms. 0.1 to 7 mol% of structural units derived from 20 α-olefins (excluding propylene), more preferably 94 to 99.9 mol% of structural units derived from propylene, and α- of 2 to 20 carbon atoms It is preferable to contain structural units derived from olefins (excluding propylene) in an amount of 0.1 to 6 mol%. Among these syndiotactic propylene polymers (A), homopolypropylene is more preferable from the viewpoint of heat resistance and the like.

The syndiotactic propylene polymer (A) according to the present invention is characterized in that the following requirements [1] to [3] are simultaneously satisfied.
[1] The syndiotactic pentad fraction (rrrr fraction) measured by ¹³ C-NMR is 85% or more.
[2] The melting point (Tm) determined by DSC is 145 ° C. or higher, and the heat of fusion (ΔH) is 40 mJ / mg or higher.
[3] The intrinsic viscosity ([η], unit dL / g) at 135 ° C. and the melt tension (MT, unit mN) at 230 ° C. satisfy the following relational expression (Eq-1).
0.25 × [η] ^4.8 ≦ MT ≦ 2.00 × [η] ^4.8 ---- (Eq-1)

Each requirement is described in detail below.
Requirement [1]
The syndiotactic propylene polymer (A) according to the present invention has a syndiotactic pentad fraction (rrrr fraction, pentad syndiotacticity) measured by NMR method of 85% or more, preferably 90% or more. More preferably, it is 93% or more, more preferably 94% or more, and the syndiotactic propylene polymer having an rrrr fraction in this range is excellent in moldability, heat resistance and transparency, and is a crystalline polypropylene. These properties are favorable and preferable. The upper limit of the rrrr fraction is not particularly limited but is 100% or less, and usually 99% or less, for example.

 This syndiotactic pentad fraction (rrrr fraction) is measured as follows.

The rrrr fraction is expressed in terms of Prrrr (absorption intensity derived from the third unit methyl group at a site where five units of propylene units are continuously syndiotactically bonded) and Pw (total methyl groups of propylene units) in ¹³ C-NMR spectrum. (Absorption intensity derived from the above) is determined by the following formula (1).
rrrr fraction (%) = 100 × Prrrr / Pw (1)

The NMR measurement is performed as follows, for example. That is, 0.35 g of a sample is dissolved by heating in 2.0 ml of hexachlorobutadiene. After this solution is filtered through a glass filter (G2), 0.5 ml of deuterated benzene is added and charged into an NMR tube having an inner diameter of 10 mm. And ¹³ C-NMR measurement is performed at 120 degreeC using the JEOL GX-500 type | mold NMR measuring apparatus. The number of integration is 10,000 times or more.

  A syndiotactic propylene polymer having an rrrr fraction in this range is preferable because it is excellent in moldability, heat resistance and mechanical properties, and has good properties as crystalline polypropylene.

Requirement [2]
The syndiotactic propylene polymer (A) according to the present invention has a melting point (Tm) obtained by differential scanning calorimetry (DSC) measurement of 145 ° C. or higher, preferably 150 ° C. or higher, more preferably 155 ° C. or higher. Further, the heat of fusion (ΔH) obtained at the same time is preferably 40 mJ / mg or more, preferably 50 mJ / mg or more, more preferably 55 mJ / mg or more.

  The differential scanning calorimetry is performed as follows, for example. About 5 mg of the sample is packed in a special aluminum pan, heated from 30 ° C. to 200 ° C. at 320 ° C./min using DSCPyris 1 or DSC 7 manufactured by PerkinElmer, and held at 200 ° C. for 5 minutes, and then from 200 ° C. to 30 ° C. This is a value obtained from an endothermic curve when the temperature is lowered at 10 ° C./min, held at 30 ° C. for another 5 minutes, and then heated at 10 ° C./min. When a plurality of peaks are detected during DSC measurement, the peak detected on the highest temperature side is defined as the melting point (Tm). Those in this range are excellent in moldability, heat resistance and mechanical properties.

Requirement [3]
The intrinsic viscosity at 135 ° C. ([η], unit dL / g) and the melt tension at 230 ° C. (MT, unit mN) are expressed by the following relational expression (Eq-1), preferably the following relational expression (Eq-2). Fulfill.
0.25 × [η] ^4.8 ≦ MT ≦ 2.00 × [η] ^4.8 ---- (Eq-1)
0.27 × [η] ^4.8 ≦ MT ≦ 1.98 × [η] ^4.8 ---- (Eq-2)

  Since the propylene resin composition containing the syndiotactic propylene polymer (A) in this range is excellent in melt tension per molecular weight, it is excellent in melt processability and as a result, the foam cell diameter at the time of foaming can be reduced. It is done. The melt tension MT is a value measured under the following conditions using a Capillograph IB manufactured by Toyo Seiki Co., Ltd.

  Capillary: Diameter 2.095 mm, Length 8.0 mm Cylinder diameter: 9.55 mm Cylinder extrusion speed: 10 mm / min Winding speed: 3.14 m / min Temperature: 230 ° C.

Propylene polymer (B)
In the propylene-based polymer (B) according to the present invention, the structural unit derived from propylene is 50 mol% to 100 mol% and the structural unit derived from one or more selected from ethylene and an α-olefin having 4 to 20 carbon atoms is 0. A propylene-based polymer (B) containing ˜50 mol% (however, 100 mol% in total). Examples of the α-olefin having 4 to 20 carbon atoms include the α-olefin described in the description of the syndiotactic propylene polymer (A). As the propylene polymer (B), for example, a known polymer as described in the pamphlet of WO 2006/123759 published by the present applicant can be used as it is.

Composition composed of component (A) and component (B) According to the present invention, the syndiotactic propylene polymer (A) is 100 to 10 parts by weight, preferably 100 to 20 parts by weight, more preferably 100 to 30 parts by weight. Part and the propylene / α-olefin copolymer (B) 0 to 90 parts by weight, preferably 0 to 80 parts by weight, more preferably 0 to 70 parts by weight [however, the sum of (A) and (B) is 100 parts by weight) in a known manner, for example, a multistage polymerization in a slurry phase, solution phase or gas phase in a continuous or batch manner, a Henschel mixer, a V blender, a riboblender, a tumbler blender, etc. A method of mixing or a method of granulating or pulverizing after mixing with a single screw extruder, twin screw extruder, kneader, Banbury mixer, etc. after mixing is adopted. Accordingly, it is possible to convert the propylene resin composition of the present invention.

  The propylene-based resin composition according to the present invention includes a weather resistance stabilizer, a heat resistance stabilizer, an antistatic agent, an anti-slip agent, an antiblocking agent, an antifogging agent, a transparent nucleating agent, as long as the object of the present invention is not impaired. Additives such as lubricants, pigments, dyes, plasticizers, anti-aging agents, hydrochloric acid absorbents and antioxidants may be blended as necessary.

  Moreover, the propylene-type resin composition which concerns on this invention may also contain the nucleating agent which is a specific arbitrary component in order to adjust foamability. In this case, for example, the nucleating agent is a dibenzylidene sorbitol-based nucleating agent, a phosphate ester-based nucleating agent, a rosin-based nucleating agent, a benzoic acid metal salt-based nucleating agent, and the like. It is preferable that there are about 0.1-1 weight part with respect to a unification composition.

  The propylene-based resin composition according to the present invention may contain at least one polymer (C) selected from polyethylene, isotactic polypropylene or styrene-based elastomer as long as the object of the present invention is not impaired. Good. As the polymer (C), a known commercially available polymer can be used as it is.

Foam The resin composition can be impregnated with the high-pressure gas by bringing the propylene-based resin composition into contact with the high-pressure gas. The form of the resin composition in contact with the high-pressure gas may be a resin molded product such as a film or sheet, or a molten propylene resin composition. A sheet shape is preferred. As a method for bringing the propylene-based resin composition into contact with the high-pressure gas, for example, the molded product of the propylene-based resin composition may be placed in a pressure-resistant container, and the high-pressure gas may be injected therein, or the molten resin may be injected. It may be put in a pressure vessel, an extrusion molding machine, an injection molding machine or the like, and high pressure gas may be injected into this.

  Examples of the high-pressure gas include carbon dioxide, nitrogen, argon, hydrogen, oxygen, butane, propane, and the like, and two or more of them can be used as necessary. For example, air may be used. Among these, carbon dioxide is preferable from the viewpoints of inertness to the resin, solubility in the resin, and handleability. When carbon dioxide is used, the concentration is usually 80% by volume or more.

  The pressure of the high-pressure gas brought into contact with the propylene-based resin composition is usually 1 MPa or more, preferably 20 MPa or more. The upper limit is not particularly limited, but is usually 50 MPa or less from the viewpoint of economy and operability. The higher the pressure, the more preferable the bubble diameter of the resulting foam tends to be small.

  The temperature of the high-pressure gas brought into contact with the propylene-based resin composition is appropriately selected depending on the form of the resin composition, and is usually 300 ° C. or lower, preferably 200 ° C. or lower. Although it does not specifically limit about a minimum, From a viewpoint of economical efficiency or operativity, it is 0 degreeC or more normally. The lower the temperature, the smaller the cell diameter of the resulting resin foam.

  The contact time between the propylene-based resin composition and the high-pressure gas is appropriately selected depending on the form of the resin, and when the resin composition melt is used, it is usually 1 second or longer, preferably 1 minute or longer, and is in the form of a film or sheet. When using a molded object, it is 1 hour or more normally, Preferably it is 3 hours or more. Although there is no particular limitation on the upper limit, after the high-pressure gas is sufficiently impregnated and diffused in the resin, and the dissolved gas in the resin reaches the saturated dissolution amount, the effect corresponding to the time is poor. Within 100 hours.

  Examples of the state of the high-pressure gas brought into contact with the propylene-based resin composition include a supercritical state or a liquid state, but a supercritical state is preferable. Note that the high-pressure gas is in a supercritical state means that the temperature and pressure of the high-pressure gas are above the critical point. In this state, the density, viscosity, diffusion coefficient, etc. are close to gas by changing the pressure. Can vary widely from liquid to liquid. The critical point of high-pressure gas varies depending on the type of high-pressure gas. For example, carbon dioxide has a critical temperature of 304.2 K and a critical pressure of 7.4 MPa, and nitrogen has a critical temperature of 126.2 K and a critical pressure of 3.4 MPa. . In the case of two or more kinds of mixed gas, a critical point exists according to the kind of gas component and the mixing ratio.

  A resin composition or a sheet-like or film-like molded product that has been contacted and impregnated with a high-pressure gas can usually be foamed by lowering the ambient pressure to about the normal pressure, that is, reducing the pressure. In the process of depressurization, usually, a part of the dissolved gas in the resin escapes to the outside of the resin composition, and the resin composition is cooled by the Joule-Thomson expansion. The pressure reduction rate may be adjusted as appropriate, but the slower the pressure reduction rate, the more the dissolved gas in the resin escapes to the outside of the resin, and the number of bubbles in the foam decreases. After completion of the decompression, the following low temperature holding is usually performed within 1 hour, preferably within 5 minutes.

  The foamed resin composition is then held at a temperature of 15 ° C. or lower, preferably 10 ° C. or lower, more preferably 5 ° C. or lower. By performing such low-temperature holding, a highly transparent resin foam can be obtained. The lower limit of the holding temperature is not particularly limited, but is usually 0 ° C. or higher from the viewpoint of operability.

  The low temperature holding time is usually 1 minute or longer, preferably 5 minutes or longer, and more preferably 1 hour or longer for the purpose of allowing the dissolved gas to sufficiently escape outside the resin composition. The upper limit of the holding time is not particularly limited, but is usually within 24 hours from the viewpoint of operability. Moreover, as a medium used for this holding | maintenance, liquids, such as cold water and oil, and gases, such as CFC, are mentioned, for example, What is necessary is just to make it contact directly or indirectly with resin.

The foam of the present invention can be obtained by the foaming method described above. The expansion ratio is usually 1.01 or more, preferably 1.03 or more, more preferably 1.05 or more, and the total light transmittance when the resin foam is a sheet having a thickness of 1 mm is: Usually, it is 10% or more, preferably 30% or more, more preferably 50% or more. The expansion ratio can be obtained by dividing the volume of the obtained resin foam by the volume of the raw resin. The total light transmittance can be measured by the method defined in ASTM D-1003.
The average cell diameter of the foam of this invention is 0.1-100 micrometers normally, Preferably it is 1-20 micrometers.

  Examples of uses of the resin foam of the present invention obtained by the above-described method include, in addition to lighting covers, signboards, building materials, antireflection films such as lenses, prisms, and displays, optical materials such as light guide plates and polarizing films. Is mentioned. In particular, the resin foam obtained by the method of the present invention can be suitably used for an optical material because of its excellent transparency.

[Example]
EXAMPLES Next, although this invention is demonstrated in detail based on an Example, this invention is not limited to this Example. The analysis method employed in the present invention is as follows.

[m1] Ethylene content, propylene content and α-olefin content in the polymer A JNM GX-400 NMR measuring apparatus manufactured by JEOL Ltd. was used. A sample of 0.35 g is dissolved by heating in 2.0 ml of hexachlorobutadiene. This solution is filtered through a glass filter (G2), 0.5 ml of deuterated benzene is added, and the solution is placed in an NMR tube having an inner diameter of 10 mm, and ¹³ C-NMR measurement is performed at 120 ° C. The number of integration is 8000 times or more. From the obtained ¹³ C-NMR spectrum, the ethylene content, propylene content and α-olefin content in the polymer were quantified.

[m2] Intrinsic viscosity ([η]))
It is a value measured at 135 ° C. using a decalin solvent. That is, about 20 mg of granulated pellets are dissolved in 15 ml of decalin, and the specific viscosity ηsp is measured in an oil bath at 135 ° C. After adding 5 ml of decalin solvent to the decalin solution for dilution, the specific viscosity ηsp is measured in the same manner. This dilution operation is further repeated twice, and the value of ηsp / C when the concentration (C) is extrapolated to 0 is obtained as the intrinsic viscosity.
[Η] = lim (ηsp / C) (C → 0)

[m3] Melting point (Tm), heat of fusion ΔH and crystallization temperature (Tc)
Using a differential scanning calorimeter DSCPyris1 or DSC7 manufactured by PerkinElmer, under a nitrogen atmosphere (20 ml / min), a sample of about 5 mg was heated to 200 ° C. and held for 10 minutes, and then cooled to 30 ° C. at 10 ° C./min. The crystallization temperature Tc was calculated from the peak of the crystallization peak at the time. Further, after maintaining at 30 ° C. for 5 minutes, the melting point was calculated from the peak of the crystal melting peak when the temperature was raised to 200 ° C. at 10 ° C./min, and the heat of fusion ΔH was calculated from the melting curve.

[m4] Stereoregularity (rrrr)
Stereoregularity (rrrr) was calculated from ¹³ C-NMR spectrum measurement.

[m5] Normal decane soluble part amount To 5 g of sample, 200 ml of n-decane was added and dissolved by heating at 145 ° C. for 30 minutes. It was cooled to 20 ° C. over about 3 hours and left for 30 minutes. Thereafter, the precipitate (n-decane insoluble part) was filtered off. The filtrate was placed in about 3 times the amount of acetone to precipitate the components dissolved in n-decane. The precipitate was filtered off from acetone and then dried. Even when the filtrate side was concentrated to dryness, no residue was observed. The amount of n-decane soluble part was determined by the following formula.
n-decane soluble part amount (wt%) = [precipitate weight / sample weight] × 100

[m6] Melt tension ( MT)
Measurement was performed under the following conditions using a Capillograph IB manufactured by Toyo Seiki Co., Ltd.
Capillary: Diameter 2.095 mm, Length 8.0 mm Cylinder diameter: 9.55 mm Cylinder extrusion speed: 10 mm / min Winding speed: 3.14 m / min Temperature: 230 ° C.

[m7] After the average cell diameter foam of the foam was impregnated in liquid nitrogen, breaking the retrieved foam. The cross section was observed with a scanning electron microscope (SEM), and the cross section image was analyzed and calculated.

[m8] Specific gravity of foam was measured using a specific gravity meter.

[m9] Film thickness of foamed film Measured using a micrometer.

[Synthesis Example 1]
-Production of syndiotactic propylene polymer (A1)-
To a glass autoclave with a capacity of 500 ml sufficiently purged with nitrogen, 250 ml of toluene was charged, propylene was circulated in an amount of 150 liters / hour, and kept at 25 ° C. for 20 minutes. On the other hand, a magnetic stirrer was placed in a 30 ml-branched flask with sufficient nitrogen substitution, 5.00 mmol of a toluene solution of methylaluminoxane (Al = 1.53 mol / l), and then dibenzylmethylene (cyclopentadiene). A toluene solution of 5.0 μmol of (enyl) (2,7-diphenyl-3,6-di-tert-butylfluorenyl) zirconium dichloride was added and stirred for 20 minutes. This solution was added to toluene in a glass autoclave in which propylene had been circulated, and polymerization was started. Propylene gas was continuously supplied at a rate of 150 liters / hour, polymerization was carried out at 50 ° C. for 10 minutes under normal pressure, and then a small amount of methanol was added to stop the polymerization. The polymer solution was added to a large excess of methanol to precipitate the polymer and dried under reduced pressure at 80 ° C. for 12 hours. As a result, 6.95 g of polymer was obtained. The polymerization activity was 7.58 kg-PP / mmol-Zr · hr. [Η] of the obtained polymer was 1.6 dL / g, Tm = 154/160 ° C., and rrrr fraction = 94%. . This operation was repeated to obtain the required amount of polymer and used in the examples. Various physical properties are shown in Tables 1 and 2.

[Synthesis Example 2]
-Production of propylene / α-olefin copolymer (B1)-
After charging 8.3 ml of dry hexane, 1-butene and 120 g of triisobutylaluminum (1.0 mmol) into a 2000 ml polymerization apparatus sufficiently purged with nitrogen, the temperature inside the polymerization apparatus was raised to 60 ° C. and propylene was used. After the pressure in the system was increased to 0.33 MPa, the system pressure was adjusted to 0.63 MPa with ethylene. Next, 0.002 mmol of di (p-chlorophenyl) methylene (cyclopentadienyl) (octamethyloctahydrodibenzofluorenyl) zirconium dichloride and 0.6 mmol of methylaluminoxane (produced by Tosoh Finechem Co.) in terms of aluminum are brought into contact with each other. The toluene solution was added to the polymerization vessel and polymerized for 20 minutes while maintaining the internal temperature at 60 ° C. and the internal pressure at 0.63 MPa with ethylene, and 20 ml of methanol was added to terminate the polymerization. After depressurization, the polymer was precipitated from the polymerization solution in 2 L of methanol and dried under vacuum at 130 ° C. for 12 hours. The obtained polymer was 97 g, and [η] = 2.2 (dL / g) measured in 135 ° C. decalin. Table 1 and Table 2 show the measured physical properties of the obtained polymer.

-Syndiotactic propylene polymer (A2)-
As the syndiotactic propylene polymer (A2), Syndiotactic polypropylene (trade name: FINAPLAS 1471, 230 ° C., MFR under a load of 2.16 kg = 4.0 g / 10 min) was used. The physical properties are summarized in Tables 1 and 2.

-Syndiotactic propylene polymer (A3)-
This is a syndiotactic propylene polymer prepared in the same manner as in Synthesis Example 1 except that the polymerization temperature is 40 ° C. The physical properties are summarized in Table 2.
-Syndiotactic propylene polymer (A4)-
The impregnated syndiotactic propylene polymer (A3) is impregnated with 0.1 phr of perhexine 25B manufactured by NOF Corporation, and then melt-kneaded at 190 ° C. and 50 rpm for 5 minutes in a lab plast mill manufactured by Toyo Seiki Co., Ltd. to obtain (A4). It was. The physical properties are shown in Table 2.

-Isotactic random propylene polymer (C1)-
Random propylene polymer (trade name: F327) manufactured by Prime Polymer was used. The physical properties are shown in Tables 1 and 2.

-Isotactic homopropylene polymer (C2)-
A propylene homopolymer (trade name: B102W) manufactured by Prime Polymer was used. The physical properties are summarized in Table 2.

Tri (2,4-di-t-butylphenyl) phosphate is added to 0.2 part by weight with respect to 100 parts by weight of the syndiotactic polypropylene (A1) obtained in Synthesis Example 1. Thereafter, using a twin screw extruder BT-30 (screw diameter 30 mm, L / D = 46) manufactured by Plastic Engineering Laboratory Co., Ltd., granulated at a set temperature of 230 ° C. and a resin extrusion rate of 3 kg / hr to obtain pellets. . Using the granulated pellet as a sample, film forming was performed at a supercritical CO ₂ content of 5% and an extrusion die temperature of 150 ° C. Table 3 shows the foam properties.

In Example 1, film formation was performed at a supercritical CO ₂ content of 11% and an extrusion die temperature of 150 ° C. Table 3 shows the foam properties.

To 75 weight of the syndiotactic polypropylene (A1) obtained in Synthesis Example 1 and 25 parts by weight of the propylene / α-olefin copolymer (B1) obtained in Synthesis Example 2, -t-Butylphenyl) phosphate is added to 0.2 parts by weight. Thereafter, using a twin screw extruder BT-30 (screw diameter 30 mm, L / D = 46) manufactured by Plastic Engineering Laboratory Co., Ltd., granulated at a set temperature of 230 ° C. and a resin extrusion rate of 3 kg / hr to obtain pellets. . Using the granulated pellet as a sample, film forming was performed at a supercritical CO ₂ content of 5% and an extrusion die temperature of 150 ° C. Table 3 shows the foam properties.

[Comparative Example 1]
Film formation was carried out using polypropylene B102 (C2) manufactured by Prime Polymer Co., Ltd. as a sample at a supercritical CO ₂ content of 5% and an extrusion die temperature of 150 ° C. Table 3 shows the foam properties.

  A foam sheet or film having excellent transparency, excellent balance between transparency and reflectivity, and a smaller foam cell diameter is provided.

Claims (5)

Syndiotactic propylene polymer (A) 100-50 parts by weight and propylene / α-olefin copolymer (B) 0-50 parts by weight [However, the total of (A) and (B) is 100 parts by weight. And a propylene-based resin composition.
Here, the syndiotactic propylene polymer (A) is
Propylene-based polymer containing 90 to 100 mol% of structural units derived from propylene and 0 to 10 mol% of structural units derived from one or more selected from ethylene and an α-olefin having 4 to 20 carbon atoms (however, the total 100 mol%) and satisfy the following requirements [1] to [3] simultaneously,
[1] The syndiotactic pentad fraction (rrrr) measured by ¹³ C-NMR is 85% or more.
[2] The melting point (Tm) determined by DSC is 145 ° C. or higher, and the heat of fusion (ΔH) is 40 mJ / mg or higher.
[3] The intrinsic viscosity ([η], unit dL / g) at 135 ° C. and the melt tension (MT, unit mN) at 230 ° C. satisfy the following relational expression (Eq-1).
0.25 × [η] ^4.8 ≦ MT ≦ 2.00 × [η] ^4.8 ---- (Eq-1)
The propylene / α-olefin copolymer (B) is
Propylene-based polymer containing 0 to 50 mol% of structural units derived from propylene and 50 to 100 mol% of structural units derived from ethylene and one or more types selected from ethylene and α-olefins having 4 to 20 carbon atoms (however, the total 100 mol%).   A foam obtained by foaming the propylene-based resin composition according to claim 1.   The foam according to claim 2, wherein an average cell diameter is 0.1 to 100 µm.   It is a foam sheet or film with a film thickness of 10-2000 micrometers, The foam of Claim 2 or 3 characterized by the above-mentioned.   A method for producing a foam, which comprises cooling the propylene-based resin composition according to claim 1 after impregnating a supercritical gas.