JPH11106520A - Antiblocking agent masterbatch and biaxially oriented polypropylene film made by using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biaxially oriented polypropylene film excellent in transparency, blocking resistance, appearance and formability by using an antiblocking agent masterbatch consisting of a crystalline polypropylene resin, an acrylic antiblocking agent comprising fine acrylic particles having a number-mean particle diameter in a specified range and a specified coefficient of variation of particle diameters, and an acid-modified polypropylene resin. SOLUTION: This masterbatch consists of 100 pts.wt. crystalline polypropylene resin, 0.5-50 pts.wt. acrylic antiblocking agent and 0.1-10 pts.wt. acid-modified polypropylene resin. The fine acrylic particles, serving as the antiblocking agent, have a number-mean particle diameter of 0.5-5 μm and a coefficient of variation of particle diameters (%), calculated by [the standard deviation of particle diameters (μm)/mean particle diameter (μm)]×100, of at most 30%. This masterbatch composition is blended with a polypropylene resin so as to provide a content of the acid-modified polypropylene resin of 0.001-0.09 pt.wt. based on 100 pts.wt. of the former polypropylene resin, and the blend is used for the production of a biaxially oriented film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antiblocking agent masterbatch for producing a biaxially oriented polypropylene film excellent in transparency, blocking resistance, appearance and moldability, and a biaxially oriented polypropylene film using the same. About.

[0002]

2. Description of the Related Art Biaxially stretched polypropylene films are widely used for food packaging and the like, but have a drawback that blocking resistance is extremely poor. In order to solve such problems, many studies have hitherto been made, including a method of adding inorganic fine particles (Japanese Patent Publication No. 52-16134) and a method of adding organic fine particles (Japanese Patent Publication No. Sho 52-16134). 50-3
No. 6262) has been proposed. However, the above method has a drawback that voids are generated at the time of stretching the film and the transparency is deteriorated. In order to solve such problems, a method of adding polymer fine particles having a specific particle size (Japanese Patent Application Laid-Open No. 9-59446), an inorganic or organic antiblocking agent having a specific particle size, and an acid-modified low molecular weight A method of adding polypropylene (JP-A-6-73202) has been proposed. However, even in a polypropylene film containing polymer fine particles of a specific particle size, the improvement of transparency is insufficient, or there is a problem that the polymer fine particles fall off at the time of winding the film and the winding roll is stained. . Further, when an acid-modified low-molecular-weight polypropylene is used in such an amount that the effect of improving transparency is exhibited, there is a problem that the moldability is inferior at the time of film formation.

[0003]

SUMMARY OF THE INVENTION The present invention relates to an antiblocking agent masterbatch for producing a biaxially oriented polypropylene film having excellent transparency, blocking resistance, appearance and moldability, and biaxial stretching using the same. It is to provide a polypropylene film.

[Means for Solving the Problems]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, the addition of an anti-blocking agent to a film was carried out in a masterbatch format. By adding a specific amount of acid-modified polypropylene, the amount of acid-modified polypropylene added to the film can be reduced to ensure film formability, and the acid-modified polypropylene suppresses the occurrence of voids in the film. The present inventors have found that a biaxially stretched polypropylene film produced using the above-mentioned anti-blocking agent masterbatch has excellent transparency, blocking resistance, appearance, and the like, and completed the present invention.

That is, according to the present invention, (A) 100 parts by weight of a crystalline polypropylene resin, (B) an average particle diameter determined from the number distribution is 0.5 to 5 μm, and a particle diameter calculated by the following equation: A masterbatch comprising 0.5 to 50 parts by weight of an acrylic antiblocking agent comprising acrylic fine particles having a coefficient of variation of 30% or less and 0.1 to 10 parts by weight of an acid-modified polypropylene resin (C). Further, the master batch, 100 parts by weight of the polypropylene-based resin, the acid-modified polypropylene resin content in the film is 0.001 to
It is a biaxially stretched polypropylene film obtained by being blended so as to be 0.09 parts by weight. Coefficient of variation of particle size (%) = standard deviation of particle size (μm) / average particle size (μm) × 100

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION

I. Anti-blocking agent master batch The anti-blocking agent master batch of the present invention is:
It comprises (A) a crystalline polypropylene resin, (B) an acrylic antiblocking agent, and (C) an acid-modified propylene resin. The components and the production method will be described below.

[0007] 1. Raw Material Component (A) Crystalline polypropylene resin (PP) The crystalline polypropylene resin used in the present invention includes:
Propylene homopolymer, or ethylene, butene,
Copolymers with other α-olefins such as hexene can be exemplified. Most preferred is a propylene homopolymer, but among copolymers, a copolymer of propylene and 40% by weight or less of another α-olefin is preferred.
Copolymers with ethylene or butene of up to 20% by weight, especially up to 20% by weight, are preferred. The copolymer may be a random copolymer or a block copolymer. These crystalline propylene polymers can be used alone or as a mixture of a plurality. The crystalline propylene-based resin of the present invention has an isotactic index (II) of 40 or more, preferably 60 or more, and particularly preferably 80 or more. In the propylene homopolymer, those having II of 90 or more, particularly 95 or more are suitable. Also, melt flow rate (MFR)
Is preferably 0.5 to 30 g / 10 min, particularly preferably 1 to 20 g / 10 min in view of film physical properties and moldability.

(B) Acrylic antiblocking agent The acrylic antiblocking agent used in the present invention is acrylic fine particles obtained by polymerizing a monomer by a method such as emulsion polymerization or suspension polymerization. Examples of the monomer include acrylic acid, methyl acrylate, methacrylic acid, methyl methacrylate, and n-butyl methacrylate. These monomers are synthesized by using one kind or a combination of plural kinds. Further, it is desirable that a crosslinkable acrylic monomer (trimethylolpropane triacrylate, ethylene glycol dimethacrylate, etc.) is copolymerized with the above monomer to give a crosslinked structure. It is also possible to use a copolymer of the above acrylic monomer and a styrene monomer such as styrene, o-styrene, m-styrene, p-styrene or a monomer such as propylene or ethylene.

The shape of the acrylic fine particles used in the present invention is preferably spherical in order to exhibit blocking resistance. The average particle size is 0.5 to 5 μm, preferably 0.1 to 5 μm.
7 to 3 μm. When the average particle size is less than 0.5 μm, the blocking resistance cannot be improved, and when the average particle size exceeds 5 μm,
Even if an acid-modified polypropylene is added, transparency and appearance are inferior. The coefficient of variation of the particle size of the acrylic antiblocking agent is 30% or less, preferably 20% or less. If it exceeds 30%, voids are generated due to the effect of coarse particles, and even if an acid-modified polypropylene is added, transparency and appearance are inferior. here,
The variation coefficient of the particle size is a value obtained by dividing the standard deviation of the particle size obtained from the number distribution by the average particle size obtained from the number distribution, that is, a value obtained by the following equation. Coefficient of variation of particle size (%) = Standard deviation of particle size (μm) / Average particle size (μm) × 100 The variation coefficient of particle size is a value indicating variation in particle size distribution. Is broad.

(C) Acid-Modified Polypropylene The acid-modified polypropylene used in the present invention is at least partially acid-modified polypropylene. The molecular weight of the acid-modified polypropylene is preferably a number average molecular weight of 800.
~ 20,000, more preferably 1,000 ~ 18,000
0. The acid value of the acid-modified polypropylene is preferably 3 to 80 mgKOH / g, more preferably 10 to 80 mgKOH / g.
60 mgKOH / g. The acid-modified polypropylene used in the present invention is synthesized by chemically adding an unsaturated carboxylic acid and / or an anhydride thereof to a low-molecular-weight polypropylene having a terminal double bond, and has a softening point of 130 ° C or higher. 170 ° C., preferably 140 to 160 ° C., and a melt viscosity at 160 ° C. of 3,000 to 20,000 c
ps, preferably 5,000 to 18,000 cps. Here, the low-molecular-weight polypropylene having a terminal double bond is preferably 1 to 1 per 1,000 carbons.
It has 0, preferably 2 to 7 terminal double bonds. If the terminal double bond is less than the above range, desired acid modification cannot be performed. Further, when the terminal double bond exceeds the above range, the heat resistance of the acid-modified low-molecular-weight polypropylene decreases, which is not preferable.

The acid modification is carried out by a melt grafting method or a solution grafting method.
C., preferably at a temperature of 130 to 240 ° C., for a reaction time of usually 0.5 to 30 hours, preferably 1 to 20 hours. The product obtained by the acid modification is preferably an unsaturated carboxylic acid and / or an anhydride thereof, preferably in an amount of 0.1 to 10%.
It is desirable that the content be 1 to 12% by weight, particularly preferably 1 to 10% by weight. As long as it is such, it may be a modified one diluted with an unmodified one. Examples of the unsaturated carboxylic acid of the acid modifier include (meth) acrylic acid, maleic acid, fumaric acid, and itaconic acid. Examples of the unsaturated carboxylic anhydride include maleic anhydride, itaconic anhydride, citraconic anhydride and the like, and among them, it is preferable to use maleic anhydride.

2. Method for Producing Antiblocking Agent Masterbatch The antiblocking agent masterbatch of the present invention is produced by blending the (A) crystalline polypropylene resin, (B) acrylic antiblocking agent, and (C) acid-modified propylene. Compounding ratio is crystalline polypropylene 100
The acrylic antiblocking agent is 0.5 to 50 parts by weight, preferably 2 to 25 parts by weight, and the acid-modified polypropylene is 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight based on parts by weight. Department. If the added amount of the acrylic anti-blocking agent is less than 0.5 part by weight, the anti-blocking property cannot be imparted. If the added amount exceeds 50 parts by weight, non-dispersion of the anti-blocking agent occurs. If the amount of the acid-modified polypropylene is less than 0.1 part by weight, the effect of improving transparency and appearance is hardly obtained, and
Exceeding the parts by weight causes poor moldability. The method for producing the anti-blocking agent master batch is described in the above (A),
After mixing (B) and (C) with a ribbon blender, a Henschel mixer, or the like, a method of melting and kneading with an extruder may be used. At that time, antioxidant, antistatic agent,
Known additives such as lubricants can be blended as appropriate.

II. Biaxially-stretched polypropylene film The biaxially-stretched polypropylene film in the present invention is obtained by mixing the above anti-blocking agent masterbatch with 100 parts by weight of a polypropylene resin, wherein the content of the acid-modified polypropylene in the film is 0.001 to 0.09 parts by weight. It is blended so that 0.001 acid-modified polypropylene
If the amount is less than part by weight, the effect of suppressing void generation cannot be obtained, and it is difficult to improve transparency. If it exceeds 0.09 parts by weight, poor moldability during film formation occurs. At the time of compounding, known additives such as antioxidants, antistatic agents and lubricants can be compounded as appropriate.

The biaxially stretched polypropylene film can be produced, for example, by mixing crystalline polypropylene and the antiblocking agent masterbatch by a ribbon blender, a Henschel mixer, or the like, and then simultaneously or sequentially biaxially stretching or inflation. Among them, the sequential secondary stretching method shown below is preferred. The polypropylene resin composition containing the anti-blocking agent master batch is melt-molded with a T die to form a raw sheet,
Thereafter, longitudinal stretching is performed using the difference in roll peripheral speed. Specifically, at a temperature of usually 90 to 150 ° C., preferably 105 to 140 ° C., the raw sheet is passed between two rolls having different rotation speeds, and 3 to 8 in the roll rotation direction (vertical direction). Times,
Preferably, it is stretched 4 to 6 times. Next, the longitudinally stretched film is transversely stretched 3 to 12 times, preferably 6 to 11 times in a tender oven.

Subsequently, this biaxially stretched film is usually
It is desirable to heat set at a temperature of 20 to 170C.
Further, for the purpose of improving printability and promoting bleeding of the antistatic agent, corona discharge treatment can be performed. The thickness of the biaxially stretched film thus obtained is not particularly limited, but is usually 200 μm or less, and
μm is preferred, and more preferably 10 to 50 μm. The biaxially stretched film of the present invention may be used as a single layer film or a laminated film. Examples of a method for obtaining a laminated film include a multilayer coextrusion method and a dry lamination method.

[0016]

The present invention will be described in more detail with reference to the following examples. In addition, the measurement of the physical property in an Example was performed by the following method. (1) MFR: JIS K6758 (230 ° C 2.1)
(6 kg load). (2) Average particle size and variation coefficient of particle size of antiblocking agent: The antiblocking agent was mixed in the anionic surfactant so as to have a concentration of about 10%. The antiblocking agent was sufficiently dispersed using an ultrasonic disperser.
The state of dispersion was observed with a microscope, and if aggregated, a surfactant was added and dispersed. The average particle diameter and the standard deviation of the obtained dispersion were measured using a Coulter Multitizer manufactured by Coulter Corporation. Here, values calculated from the number distribution were used for the average particle diameter and the variation coefficient. (3) HAZE: Based on ASTM-D-1003,
The measurement was performed by stacking four films. (4) Image sharpness: Measured using an image clarity measuring device manufactured by Suga Test Instruments. The larger the value, the better the image clarity.

(5) Blocking property: Two films are stacked so that the contact area of the ^two films is 40 cm ² , placed between two glass plates, and left under a load of 2 kg in an atmosphere of 40 ° C. for 24 hours. Thereafter, the film was peeled off using a tensile tester at a tensile speed of 150 mm / min, and the maximum load was read to evaluate. (6) Appearance: The state of occurrence of voids in the film was observed at a magnification of 100 with a phase contrast microscope, and the degree of occurrence was visually evaluated according to the following criteria. ◎: almost no voids ○: slight voids △: many voids ×: quite large voids

(7) Formability: Evaluation was made using the fluctuation of the cylinder temperature of the extruder as an index when forming a biaxially stretched film. ：: No temperature fluctuation Δ: Temperature slightly fluctuated, but no problem in molding X: Temperature fluctuation was severe, and molding failure occurred (8) Anti-blocking agent falling off property: 20
The amount of generated antiblocking agent powder adhering to the take-up roll when formed into a length of 000 m was visually evaluated. ：: No generation of powder △: Generation of powder is recognized ×: Generation of powder is extremely large

Example 1 0.18 parts by weight of BHT as an antioxidant and pentaerythrityl-tetrakis [100 parts by weight of a crystalline polypropylene (PP) homopolymer having an MFR of 2.3 and an II of 96.2 are used. 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (Ir1010)
0.05 parts by weight, 0.1 part by weight of calcium stearate as a neutralizing agent, and crosslinked PMMA fine particles having an average particle size of 2.5 μm and a variation coefficient of particle size of 16.6% as an acrylic antiblocking agent (AB agent) 25 parts by weight and 1.0 part by weight of acid-modified polypropylene (maleic anhydride-modified PP, number average molecular weight 15,000, acid value 26 mg KOH / g) were added, and mixed with a Henschel mixer.
Granulation was performed with a twin-screw extruder to obtain an antiblocking agent masterbatch (AB agent MB resin).

On the other hand, BH as an antioxidant was added to 100 parts by weight of crystalline PP having an MFR of 2.3 and an II of 96.2.
0.18 parts by weight of T, 0.05 parts by weight of pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (Ir1010), and 0.1% of calcium stearate as a neutralizing agent. 1 part by weight and 1.1 parts by weight of a polyoxyethylene alkylamine fatty acid ester as an antistatic agent were added, mixed with a Henschel mixer, and then granulated with a 65 mmφ extruder. After adding 0.5 part by weight of the AB agent MB resin to 100 parts by weight of the above resin and mixing with a ribbon mixer,
It was melted and extruded at a resin temperature of 80 ° C., quenched with a cooling roll of 30 ° C. to form a sheet-like film, and sequentially stretched 5 times in the longitudinal direction and 10 times in the transverse direction to finally obtain a stretched film of 20 μm. Table 1 shows the composition of AB agent, MB resin and stretched film.
And Table 2 shows the properties of the obtained stretched film.

Examples 2 to 4 The amount of acid-modified PP added to MB resin, the amount of AB agent added to MB resin or the amount of MB resin added to stretched film was changed as shown in Tables 1 and 2. Except for the above, a biaxially stretched film was obtained in the same manner as in Example 1. AB agent, MB resin,
The composition of the stretched film is shown in Tables 1 and 2, and the properties of the obtained stretched film are shown in Table 3.

Example 5 The type of AB agent was changed to crosslinked methyl methacrylate-styrene copolymer fine particles (styrene content 20%, average particle size 1.8 μm,
(Coefficient of variation of particle size: 20%), and a stretched film was obtained in the same manner as in Example 1 except that the addition amount was as shown in Tables 1 and 2. Tables 1 and 2 show the compositions of the AB agent, MB resin and stretched film, and Table 3 shows the properties of the obtained stretched film.

Comparative Examples 1-2 The same method as in Example 1 except that the addition of the acid-modified PP to the MB resin was not added and the amount of the MB resin added to the stretched film was as shown in Table 2. To obtain a biaxially stretched film. Tables 1 and 2 show the compositions of the AB agent, MB resin and stretched film, and Table 3 shows the properties of the obtained stretched film.

Comparative Example 3 A stretched film was formed in the same manner as in Example 1 except that the amount of the acid-modified PP added to the MB resin was changed to 15 parts by weight and the amount of the MB resin added to the stretched film was changed. . The cylinder temperature of the extruder fluctuated, the discharge amount became unstable, and a film could not be obtained.

Comparative Example 4 0.18 parts by weight of BHT as an antioxidant and pentaerythrityl-tetrakis [3- (3,5-di) were added to 100 parts by weight of crystalline PP having an MFR of 2.3 and an II of 96.2. -T-butyl-4-hydroxyphenyl) propionate] (Ir1010) 0.05 part by weight, calcium stearate 0.1 part by weight as a neutralizing agent, and an average particle size of 2. as an acrylic antiblocking agent (AB agent). 5μ
m, crosslinked PMMA fine particles 2 having a coefficient of variation of particle diameter of 16.6%
5 parts by weight, acid-modified polypropylene (maleic anhydride-modified PP, number average molecular weight 15,000, acid value 26 mg KOH /
g) 1.0 part by weight and 1.1 parts by weight of a polyoxyethylene alkylamine fatty acid ester as an antistatic agent were added, mixed with a Henschel mixer, and then granulated with a 65 mmφ extruder. The resin was melted and extruded at a resin temperature of 280 ° C., quenched by a cooling roll at 30 ° C. to form a sheet-like film, and sequentially stretched 5 times in the longitudinal direction and 10 times in the transverse direction to form a stretched film. The cylinder temperature of the extruder fluctuated, the discharge amount became unstable, and a film could not be obtained.

Comparative Example 5 The type of the antiblocking agent was changed (crosslinked PMMA fine particles, average particle size 1.9 μm, coefficient of variation of particle size 37.3).
%) And a blended formulation shown in Table 1 was obtained in the same manner as in Example 1. Tables 1 and 2 show the compositions of the AB agent, MB resin and stretched film, and Table 3 shows the properties of the obtained stretched film.

Comparative Example 6 The type of the antiblocking agent was changed to amorphous silica (average particle size: 4.5 μm), and a stretched film was obtained in the same manner as in Example 1 by using the formulation shown in Table 1. Tables 1 and 2 show the compositions of the AB agent, MB resin and stretched film, and Table 3 shows the properties of the obtained stretched film.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

As is clear from Table 3, the biaxially stretched polypropylene films using the antiblocking agent masterbatch of the present invention obtained in Examples 1 to 5 have excellent transparency, blocking properties, appearance and appearance. It showed moldability and was of high quality. On the other hand, the stretched film obtained in Comparative Example 1 has slightly poor blocking properties and inferior appearance, and the stretched film obtained in Comparative Example 2 has good blocking properties, but has poor transparency and appearance. The stretched film obtained in Comparative Example 5 is inferior in transparency and appearance due to the wide particle size distribution of the AB agent, and the stretched film obtained in Comparative Example 6 is inferior in transparency, blocking property and appearance. , All were of low quality.

[0032]

The master batch of the anti-blocking agent of the present invention has a constitution in which a specific amount of an acrylic anti-blocking agent and a specific amount of an acid-modified polypropylene are blended with crystalline polypropylene, so that a biaxially stretched polypropylene film using the same is used. Is excellent in moldability such as excellent transparency, appearance and blocking resistance, and does not cause poor extrusion during film formation. Further, the biaxially stretched polypropylene film of the present invention is a film having good operability without generating stain on the roll at the time of winding, and is a stretched film having industrially extremely usefulness as various packaging films. .

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 33:08 23:26) B29K 23:00

Claims (2)

[Claims] (A) crystalline polypropylene resin 10
0 parts by weight, (B) an acrylic antimicrobial particle composed of acrylic fine particles having an average particle diameter determined from the number distribution of 0.5 to 5 μm and a coefficient of variation of the particle diameter calculated by the following formula of 30% or less. An antiblocking agent masterbatch comprising 0.5 to 50 parts by weight of a blocking agent and 0.1 to 10 parts by weight of an acid-modified polypropylene resin (C). Coefficient of variation of particle size (%) = standard deviation of particle size (μm) / average particle size (μm) × 100 2. An average particle diameter obtained from (A) 100 parts by weight of a crystalline polypropylene resin and (B) a number distribution with respect to 100 parts by weight of the polypropylene resin is 0.5.
0.5 to 50 parts by weight of an acrylic antiblocking agent composed of acrylic fine particles having a particle diameter variation coefficient calculated by the following formula of 30% or less and 0.5 to 50 parts by weight of an acid-modified polypropylene resin (C). An antiblocking agent masterbatch consisting of 1 to 10 parts by weight was prepared by adding an acid-modified polypropylene resin content in a film of 0.001 to 10 parts by weight.
A biaxially stretched polypropylene film obtained by being blended so as to be 0.09 parts by weight. Coefficient of variation of particle size (%) = standard deviation of particle size (μm) / average particle size (μm) × 100