JP2001072812A - Polypropylene resin composition and film comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polypropylene resin composition which consists mainly of propylene polymer particles obtained using a highly active catalyst and having a large average particle diameter and a narrow particle diameter distribution and can produce films that are good in appearances and in the dispersion of anti-blocking agents, and to provide a film comprising the polypropylene resin composition. SOLUTION: This polypropylene resin composition comprises 100 pts.wt. of propylene polymer particles having an average particle diameter of 500 to 1,200 μm and a particle diameter distribution of 0.2 to 0.4, and 0.01 to 0.7 pt.wt. of synthetic silica having a fine pore volume of <=1 ml/g, an oil absorption of <=150 ml/100 g, a bulk density of >=0.20 g/cm3, and an average particle diameter of 1 to 4 μm measured with a Coulter counter. The polypropylene resin composition is used for forming a film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polypropylene resin composition and a film comprising the same. More specifically, the present invention relates to a polypropylene resin composition which is mainly composed of propylene polymer particles having a large average particle diameter and a narrow particle diameter distribution, and which is suitable as an extrusion molding material, and a film comprising the same.

[0002]

2. Description of the Related Art Polyolefin films have been used in a wide variety of applications. For example, it is widely used as a packaging material for various articles such as food packaging. Especially polypropylene film has mechanical properties and transparency,
It is widely used mainly in the field of food packaging since it has excellent optical properties such as gloss and food hygiene such as water vapor barrier property and odorlessness.

However, since the polypropylene film itself has poor blocking resistance, when the films are stacked, so-called blocking occurs in which the films come into close contact with each other, and has a drawback that the workability of packaging and the like is remarkably reduced. For this reason, as a method of preventing blocking of the polypropylene film, a method of blending an inorganic fine powder represented by silicon dioxide in the film, or an organic fine particle such as a crosslinked polymer, as a so-called anti-blocking agent, or the like. Generally practiced.

As a method of incorporating an anti-blocking agent into polypropylene, industrially, an anti-blocking agent is added to polypropylene particles obtained by polymerization, and the mixture is first mixed with a mixer at a temperature lower than the melting point of the polypropylene. And then melt-kneaded at a temperature equal to or higher than the melting point of the polypropylene.

[0005] Catalysts conventionally represented by titanium trichloride-organoaluminum compounds which are industrially used have low polymerization activity, and propylene polymers obtained by polymerizing propylene in the presence of such catalysts have an average The particle size was relatively small and the particle size distribution was wide. In such a propylene polymer, good dispersibility was obtained in a low concentration region where the content of the antiblocking agent was 1% by weight or less.

However, a propylene polymer obtained by using a highly active catalyst such as a supported catalyst using an inorganic solid as a carrier or a metallocene catalyst developed later has a large average particle diameter and a narrow particle diameter distribution. In the case of a conventionally known anti-blocking agent such as silica which has been widely used in film applications, a silica aggregate is generated in the mixing and granulating step with polymer particles, and the anti-blocking effect is not sufficiently exhibited. In addition, there has been a problem that the appearance of the film is significantly impaired.

As an attempt to solve such a problem, for example, the methods described in JP-A-5-9349 and JP-A-8-81591 are known. JP-A-5-9349 proposes a polypropylene composition comprising a specific property of a particulate polypropylene and a specific property of a silicon dioxide powder and a specific property of an aluminosilicate powder as antiblocking agents. However, aluminosilicate has a problem that the film surface is easily damaged when the films are rubbed against each other due to its hardness. Japanese Patent Application Laid-Open No. 8-81591 proposes a polyolefin composition comprising a specific property of olefin polymer particles and a silicon dioxide powder of trade name Siloid 55 as an antiblocking agent. Additional tests showed that the dispersion of the antiblocking agent was not sufficient.

[0008]

DISCLOSURE OF THE INVENTION The present invention has a large average particle size and a large particle size as represented by a propylene polymer obtained by using a supported catalyst or a metallocene catalyst using an inorganic solid as a carrier. It is an object of the present invention to provide a polypropylene resin composition mainly composed of propylene polymer particles having a narrow distribution and capable of producing a film having a good dispersion and appearance of an antiblocking agent, and a film comprising the same.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, a resin composition containing a specific amount of synthetic silica having a specific property has been obtained by dispersing the synthetic silica. The inventors have found that a film excellent in properties and appearance is provided, and have reached the present invention.

That is, the present invention relates to propylene polymer particles having a distribution of particle diameters, the average particle diameter of which is 50%.
The following properties (a) to 100 parts by weight of propylene polymer particles having a particle size distribution of 0 to 1200 μm and a standard deviation / average particle size of 0.2 to 0.4 are shown below.
Provided is a polypropylene resin composition containing 0.01 to 0.7 parts by weight of a synthetic silica satisfying (d). (A) The average particle size measured by the Coulter counter is 1
４4 μm. (B) The pore volume is 1 ml / g or less. (C) The oil absorption is 150 ml / 100 g or less. (D) The bulk specific gravity is 0.20 g / cm ³ or more.

Further, the present invention provides the above polypropylene resin composition, wherein the propylene polymer is a propylene / ethylene random copolymer or a propylene / ethylene / butene-1 copolymer.

Further, the present invention provides the above polypropylene resin composition, further comprising a lubricant in an amount of 0.04 to 1 part by weight based on 100 parts by weight of the propylene polymer particles.

Further, the present invention provides a T-die film obtained by melt-extrusion molding any one of the above-mentioned polypropylene resin compositions by a T-die method. Further, the present invention provides an inflation film obtained by melt-extrusion molding any one of the polypropylene resin compositions by a tubular method.

[0014]

Embodiments of the present invention will be described below. The polypropylene resin composition of the present invention is mainly composed of propylene polymer particles and contains synthetic silica.

(1) Propylene polymer particles The propylene polymer particles used in the polypropylene resin composition of the present invention have an average particle diameter of 500 to 1200.
μm, preferably 500 to 1000 μm, and a particle size distribution represented by a coefficient of variation (= standard deviation / average particle size) is 0.2 to 0.4, preferably 0.3 to 0.4. If the average particle diameter of the polymer exceeds 1200 μm, the dispersion tends to be deteriorated even when the synthetic silica having the specific properties of the present invention is blended. On the other hand, for polymer particles of less than 500 μm, conventional silica can be applied,
It is not an object of the present invention. When the particle size distribution of the polymer exceeds 0.4, conventional silica can be used and is not the object of the present invention. If the particle diameter fraction is less than 0.2, it is not easy to improve the dispersibility of the synthetic silica even with the present invention.

In the present invention, the average particle size and the particle size distribution are values measured using a sieve. The propylene polymer particles are sieved to a diameter of 53 μm (m ₁ ), 105 μm
(M ₂ ), 149 μm (m ₃ ), 250 μm (m ₄ ), 2
97 μm (m ₅ ), 350 μm (m ₆ ), 420 μm (m
₇ ), 500 μm (m ₈ ), 600 μm (m ₉ ), 710
μm (m ₁₀ ), 840 μm (m ₁₁ ), 1000 μm (m
₁₂ ), 1180 μm (m ₁₃ ), 1400 μm (m ₁₄ ),
The weight distribution (f ₁ , f ₂ ,... F ₁₅ ) of the unsieved residue of each sieve when sieved with a 1680 μm (m ₁₅ ) sieve was measured according to the following formula. The representative value of the particle size of each class is the center value between sieves (for example, the representative value of the particle size of m ₈ is the center value of 500 μm and 460 μm of 420 μm).
And

Average particle size = (m ₁ * f ₁ + m ₂ * f ₂ +.)
.. + M ₁₅ * f ₁₅ ) where f ₁ + f ₂ +... + F ₁₅ = 1 Particle size distribution = standard deviation / average particle size

[0018]

(Equation 1)

Where S ² = [(m ₁ ² * f ₁ + m ₂ ² * f ₂ +...
・ + M ₁₅ ² * f ₁₅ ) − (average particle diameter) ² ]

The method for producing the propylene polymer particles of the present invention having the specific average particle diameter and the particle diameter distribution is not particularly limited, and may be obtained by any method. When a highly active catalyst such as a so-called supported catalyst or a metallocene catalyst having a carrier as a carrier is used, specifically, when a catalyst having a propylene polymerization amount of 10000 g or more per 1 g of the catalyst is used, such large average particles are used. Propylene polymer particles having a diameter and a narrow particle size distribution are obtained.

Examples of the propylene polymer include propylene homopolymer, propylene and α-olefin having a propylene content of 80% by weight or more, preferably 90% by weight or more, using α-olefin having 2 to 8 carbon atoms other than propylene as a comonomer. Or a random copolymer of two or more of the above. Among them, in the present invention, the propylene content of which is an α-olefin having 2 to 8 carbon atoms excluding propylene as a comonomer is 8%.
A binary copolymer of propylene and α-olefin in an amount of 0% by weight or more, preferably 90% by weight or more is preferred, and those in which the α-olefin is ethylene and / or butene-1 are particularly preferred.

The MFR of the propylene polymer particles of the present invention is not particularly limited, but is preferably 3 to 15 g / 1.
0 minutes.

(2) Synthetic Silica The synthetic silica used in the polypropylene resin composition of the present invention satisfies the following properties (a) to (d).

(A) Average Particle Diameter The synthetic silica has an average particle diameter of 1 to 4 μm, preferably 2 to 4 μm. The average particle diameter here is a value measured by the Coulter counter method (AP · 30 μm).

If the average particle size exceeds 4 μm, the transparency (transparency) of the obtained film is remarkably deteriorated, which is not preferable. On the other hand, when the thickness is less than 1 μm, the film slippage during winding and the blocking resistance are poor, which is not preferable.

(B) Pore Volume The synthetic silica has a pore volume of 1 ml / g or less, preferably 0.5 to 1 ml / g. Here, the pore volume is a value measured by the N ² adsorption method. Those having a pore volume of more than 1 ml / g tend to aggregate when mixed with propylene polymer particles,
E) and poor dispersibility. If it is less than 0.5 ml / g, the silica particles become too hard, and when the films rub against each other, the scratches tend to be remarkable. The pore volume is
It is considered to indicate the structure of the primary particles of the synthetic silica. If this value is large, the primary particles have a high surface energy and tend to aggregate when mixed with the propylene polymer particles.

(C) Oil Absorption The synthetic silica has an oil absorption of 150 ml / 100 g.
Hereinafter, it is preferably 80 to 150 ml / 100 g.
If the oil absorption exceeds 150 ml / 100 g, FE is likely to occur. The oil absorption here refers to JIS-K510
It is a value measured according to 1-19. The oil absorption indicates the structure of the synthetic silica similarly to the pore volume, but is considered to be a property mainly due to the three-dimensional aggregate structure from the properties such as the oil adsorption. That is, if this value is large, it means that the synthetic silica alone tends to be present as an aggregate.

(D) Bulk specific gravity The synthetic silica has a bulk specific gravity of 0.20 g / cm ^3.
As mentioned above, it is preferably 0.25 to 0.5 g / cm ³ .
Here, the bulk specific gravity is a value measured according to JIS-K6220-6.8. If it is less than 0.20 g / cm ³ , it tends to agglomerate when mixed with the propylene polymer particles, which becomes FE and deteriorates the appearance.

As a method for producing the synthetic silica having such specific properties and used in the present invention, any conventionally known method such as a wet method and a dry method can be used. In particular, the wet method is preferable because the physical properties can be easily controlled. Wet method synthetic silica forms a primary particle after mixing sodium silicate and sulfuric acid made of high-purity silica sand as raw materials, forms primary particles, and forms a three-dimensional silica aggregate by a sol-gel polymerization reaction It can be obtained by: In this process, synthetic silica having desired properties can be obtained by changing the conditions for forming the primary particles. It is difficult and unsuitable to obtain the above-mentioned properties of naturally occurring silica. As the synthetic silica having such specific properties and used in the present invention, commercially available products can also be used. The synthetic silica that can be used in the present invention only needs to contain at least 40% by weight of silicon dioxide in its crystal structure, and may be magnesium silicate, aluminum silicate, or calcium aluminum silicate.

The synthetic silica may be subjected to various surface treatments (for example, hydrophobization, pH adjustment, impregnation with an organic stabilizer, etc.) as long as the above properties are satisfied.

The synthetic silica is incorporated in an amount of 0.01 to 0.7 parts by weight based on 100 parts by weight of the propylene polymer particles.
Preferably it is 0.05 to 0.7 parts by weight. More preferably, it is 0.05 to 0.4 parts by weight in a T-die film, and 0.2 to 0.4 parts by weight in a blown film.
5 to 0.7 parts by weight. If the amount is less than the above range,
It is not preferable because the anti-blocking property of the film is inferior. On the other hand, if it exceeds the above range, the transparency of the film is impaired, which is not preferable.

(3) Lubricant The polypropylene resin composition of the present invention preferably further contains a lubricant. Examples of the lubricant include fatty acids such as stearic acid and palmitic acid; metal salts of fatty acids such as calcium stearate and magnesium stearate; fatty acid amides such as oleic amide and erucamide; and derivatives containing other fatty acid forming groups. Can be.
Among them, particularly preferred are fatty acid amides.
The amount of the fatty acid amide is not particularly limited, but is preferably 0.04 to 100 parts by weight of the propylene polymer particles.
To 1 part by weight, more preferably about 0.04 to 0.4 parts by weight for a T-die film, and about 0.2 to 0.8 parts by weight for an inflation film. By blending the fatty acid amide within the above range with the polypropylene resin composition of the present invention, the slip required for the film slip and the post-processing step is improved, and the advantage that the opening property is improved in the blown film is obtained. Can be

(4) Other Ingredients In the polypropylene resin composition of the present invention, additives, inorganic fillers and the like can be appropriately compounded as needed within a range not to impair the object of the present invention. Preferred additives that can be added include, for example, phosphorus-based antioxidants having a molecular weight of 500 or more, phenolic antioxidants, and inorganic fillers.

As the antioxidant, for example, tetrakis- [methylene-3- (3 ′, 5′-di-tert-butyl-
4'-hydroxyphenyl) propionate] methane,
1,3,5-trimethyl-2,4,6-tris (3,5
-Di-t-butyl-4-hydroxybenzyl) benzene, 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanate, tris (3,5-di-t -Butyl-4-hydroxyphenyl) isocyanurate, tetrakis- (2,4-di-t)
-Butylphenyl) -4,4'-biphenylene-diphosphite and the like. These alone,
Alternatively, two or more kinds can be used in combination.

The amount of the antioxidant is not particularly limited, but is preferably about 0.03 to 0.5 part by weight based on 100 parts by weight of the propylene polymer particles. The combination of these antioxidants is extremely effective for stability during film formation and film use.

(5) Method for Preparing Polypropylene Resin Composition The method for preparing the polypropylene resin composition of the present invention includes a method of adding synthetic silica directly to propylene polymer particles and a method of adding a master batch of the synthetic silica. No.

When a masterbatch is used, since the masterbatch must contain a high concentration of synthetic silica, the propylene polymer particles used in the matrix of the masterbatch have an average particle diameter of less than 500 μm and a particle size distribution of less than 500 μm. A wide one is preferable, and the MFR is 3 to 15
It is preferably about g / 10 minutes.

In conventional silica, when the concentration is high, the dispersibility is poor, and the quality of the master batch is unstable. However, when synthetic silica satisfying the specific properties of the present invention is used, a stable dispersion master batch can be obtained in a concentration range of about 4 to 8% by weight.

The polypropylene resin composition of the present invention can be obtained by mixing propylene polymer particles with synthetic silica, followed by melt-kneading. Known methods such as a tumbler mixer, a super mixer, a Henschel mixer, a screw blender, and a ribbon blender can be used for the mixing. Melt kneading is not particularly limited as long as it is a method of melting and kneading at a temperature equal to or higher than the melting point of the propylene polymer particles using, for example, a melt extruder or a Banbury mixer.

The melt-kneading method can be easily carried out using either a single-screw extruder or a twin-screw extruder, but a twin-screw extruder is suitable for more effectively dispersing the synthetic silica.

(6) Film A film according to another aspect of the present invention is obtained by melt-extruding the above polypropylene resin composition. The method for producing the film is not particularly limited, but is preferably used for producing an unstretched film (T-die film or blown film) obtained by melt extrusion molding by a T-die method or a tubular method. As the molding conditions of the T-die molding method or the tubular method (inflation molding method), conventionally known molding conditions for the polypropylene film can be adopted.

The thickness of the obtained film can be appropriately selected according to the intended use, and is not particularly limited.
It is about 0 to 60 μm. Such a film is suitably used for a wide range of applications such as food packaging materials, stationery and miscellaneous goods packaging materials.

[0043]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the invention. Table 1 shows properties of silica used as an antiblocking agent in the following Examples and Comparative Examples.

[0044]

[Table 1]

P-763: Mizukasil P-763 (manufactured by Mizusawa Chemical Industry Co., Ltd.) M-302: Mizpearl M-202 (manufactured by Mizusawa Chemical Industry Co., Ltd .;
Spherical) M-204: Mizpearl M-204 (manufactured by Mizusawa Chemical Industries, Ltd .;
SB / S200: Silo block S200 / Grace (manufactured by Davison) SB / S500: Silo block S500 / Grace (manufactured by Davison) SB / M250: Silo block M250 / Grace (manufactured by Davison; impregnated with fatty acid amide) SIH505: SILOHOBIK 505 (manufactured by Fuji Silysia; polyalkylsiloxane treated) SIH704: Silohobic 704 (manufactured by Fuji Silysia; treated with polyalkylsiloxane) P-707: Mizukasil P-707 (manufactured by Mizusawa Chemical Industries) P-709 : Mizukasil P-709 (manufactured by Mizusawa Chemical Industries) P-766: Mizukasil P-766 (manufactured by Mizusawa Chemical Industries) SY550: Thylsia 550 (manufactured by Fuji Silysia)

[0046]

Examples 1 to 14 Propylene / ethylene random copolymer particles obtained with a supported catalyst (ethylene content =
4 wt%, average particle size = 750 μm, standard deviation / average particle size = 0.29) 100 parts by weight of silica of the type and amount described in Table 2 as an antiblocking agent, and 2,6-di as an additive -T-butyl-4-methylphenol (BHT) / calcium stearate (Cas
t) / erucamide (E. Amide) (content =
0.1 / 0.05 / 0.1 parts by weight) to prepare a polypropylene resin composition.

That is, the propylene polymer particles, silica, and additives were mixed in a 20 L Henschel mixer for 50 hours.
The mixture was mixed at 0 rpm for 2 minutes, and then melt-kneaded with a twin-screw extruder (manufactured by Ikegai Seisakusho Co., Ltd., trade name “PCM30”) adjusted to 220 ° C. to obtain pellets. Using these pellets, extruded at 240 ° C. using a T-die molding machine with a diameter of 30 mm,
The film was rapidly cooled by a cooling roll having a surface temperature of 30 ° C. to obtain a film having a thickness of 25 μm. Spots (fish eyes: abbreviated as FE) having a diameter of 0.1 mm or more due to silica aggregates were visually counted (unit: pieces / m ² ). The surface appearance was visually observed and evaluated according to the following criteria. Table 2 shows the results.

(Visual Appearance) Good: No fine fish-eye inferior: Fine fish-eye on one surface of film poor *: No fine fish-eye, but smell due to silica

[0049]

Examples 15 to 23 100 parts by weight of propylene / ethylene random copolymer particles (ethylene content = 4 wt%, average particle size = 750 μm, standard deviation / average particle size = 0.29) obtained by the supported catalyst were used. , Silica of the kind and amount described in Table 3 as an anti-blocking agent, and BHT / Cast / oleic acid amide (O. Amide) as an additive (blending amount = 0.1 / 0.05 / 0.
4 parts by weight) to prepare a polypropylene resin composition.

That is, the propylene polymer particles, silica and additives were mixed in a 20 L Henschel mixer for 500 hours.
The mixture was mixed at rpm for 2 minutes, and then melt-kneaded with a twin-screw extruder adjusted to 220 ° C. to obtain pellets. The pellets were extruded at 210 ° C. using a water-cooled inflation molding machine having a diameter of 40 mm, and rapidly cooled with water at a temperature of 20 ° C.
A 5 μm thick tubular film was obtained. Butts (FE) having a diameter of 0.1 mm or more due to silica aggregates were visually counted. The surface appearance was visually observed and evaluated. Table 3 shows the results.

[0051]

Examples 24 to 25 Homopropylene polymer particles having an average particle diameter of 400 μm and a standard deviation / average particle diameter of 0.7 (M
FR = 10g / 10min) 95% by weight of "SIH505"
5 parts by weight, BHT 0.1 parts by weight, Cast 0.0
8 parts by weight of a master batch obtained by blending 5 parts by weight and melt-kneading was blended with 92 parts by weight of the propylene polymer particles used in Examples 10 to 18 together with an antioxidant, a neutralizing agent, and a slip agent. After mixing well in a plastic bag, 200
Pellets were obtained with a twin-screw extruder adjusted to ° C.

Using these pellets, a 30 mm diameter T
It was extruded at 200 ° C. using a die forming machine, and rapidly cooled with a cooling roll at a temperature of 30 ° C. to obtain a 25 μm thick film. Butts (FE) having a diameter of 0.1 mm or more due to silica aggregates were visually counted. The surface appearance was visually observed and evaluated. Table 4 shows the results.

[0053]

Comparative Examples 1 to 6 Films were obtained in the same manner as in Examples 1 to 14, except that the type and amount of silica used as the antiblocking agent were changed to those shown in Table 5. Example 1
FEs were visually counted as in # 14. The surface appearance was visually observed and evaluated. Table 5 shows the results.

[0054]

Comparative Examples 7 to 10 Except that the type and amount of silica used as an antiblocking agent were changed to those shown in Table 6,
A film was obtained in the same manner as in Examples 15 to 23. FEs were counted visually as in Examples 15 to 23. The surface appearance was visually observed and evaluated. Table 6 shows the results.

[0055]

[Table 2]

[0056]

[Table 3]

[0057]

[Table 4]

[0058]

[Table 5]

[0059]

[Table 6]

[0060]

According to the present invention, a propylene polymer having a large average particle size and a narrow particle size distribution obtained by using a highly active catalyst such as a supported catalyst or a metallocene catalyst using an inorganic solid as a carrier. By blending the particles with synthetic silica having a specific property, a polypropylene resin composition capable of producing a film having good dispersion and appearance of the synthetic silica and a film comprising the same can be obtained.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 5/09 C08K 5/09 // B29K 23:00 B29L 7:00 (72) Inventor Tadashi Sezume Mie 1 Toho-cho, Yokkaichi-shi, Japan F-term in Material Development Center of Japan Polychem Corporation 4F071 AA15X AA20 AA21X AA76 AB26 AC09 AC10 AD02 AD06 AE11 AF53 AH04 BA01 BB06 BB09 BC01 4F207 AA04E AA11E AA12E AB07 AB17 ACO01 AG01 KA17 KA19 KF01 KL84 4J002 BB121 BB141 BB151 DJ016 EF057 EG037 EP017 FA081 FA086 FD177 GG02

Claims (5)

[Claims] 1. A propylene polymer particle having a distribution of particle diameters, wherein the average particle diameter is 500 to 1200 μm,
In addition, the particle size distribution represented by the standard deviation / average particle size is 0.
A polypropylene resin composition containing 0.01 to 0.7 parts by weight of synthetic silica satisfying the following properties (a) to (d) based on 100 parts by weight of propylene polymer particles of 2 to 0.4: . (A) The average particle size measured by the Coulter counter is 1
４4 μm. (B) The pore volume is 1 ml / g or less. (C) The oil absorption is 150 ml / 100 g or less. (D) The bulk specific gravity is 0.20 g / cm ³ or more. 2. The method according to claim 1, wherein the propylene polymer is propylene.
Ethylene random copolymer or propylene / ethylene /
2. A butene-1 copolymer.
The polypropylene resin composition according to the above. 3. The polypropylene resin composition according to claim 1, further comprising 0.04 to 1 part by weight of a lubricant based on 100 parts by weight of the propylene polymer particles. 4. A T-die film obtained by melt-extruding the polypropylene resin composition according to claim 1 by a T-die method. 5. A blown film obtained by melt-extruding the polypropylene resin composition according to claim 1 by a tubular method.