JP3040565B2 - Polyolefin composition for film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin composition for a film containing a specific anti-blocking agent for a polyolefin film comprising calcium carbonate. To provide a polyolefin film.

[0002]

2. Description of the Related Art Polyolefins are widely used as industrial products for various uses. In particular, polyolefin films such as polypropylene films are most widely used as various packaging materials. As is well known, this type of polyolefin film is susceptible to blocking due to its tackiness, which not only impairs workability in the production of the film and further higher-order processing thereof, but also, for example, in the use of the film for packaging. In the case of packaging, troubles such as poor opening of the bag are likely to occur. Therefore, this type of film is usually subjected to anti-blocking treatment, and finely divided silica, zeolite, calcium carbonate or kaolin clay is typically known and used as an anti-blocking agent.

[0003] On the other hand, excellent transparency is required as a quality characteristic of a polyolefin film. However, the transparency and the blocking resistance are contradictory quality characteristics, and the blocking resistance of the polyolefin film is improved. When a large amount of an antiblocking agent is used for the purpose, the transparency of the polyolefin film decreases with an increase in the amount of the antiblocking agent, and both of these blocking resistance and transparency can be effectively satisfied. As a modifying additive, any of the conventional inorganic powders has disadvantages. For example, conventionally used kaolin clay, because the particle shape has a plate-like structure, using as a polyolefin film anti-blocking agent,
Since sufficient unevenness could not be formed on the surface of the polyolefin film, good blocking resistance could not be obtained unless it was used in a large amount. As a result, only a polyolefin film having insufficient transparency was obtained.
Similarly, when fine silica powder is used, since the basic particles are extremely fine, a good polyolefin film can be obtained from the viewpoint of transparency, but sufficient irregularities are formed on the surface of the polyolefin film even when used in large amounts. Therefore, a sufficient polyolefin film could not be obtained from the viewpoint of a blocking prevention function. In addition, when zeolite powder is used, kaolin clay, compared with finely divided silica, relatively good transparency, although a polyolefin film having blocking resistance can be obtained, since zeolite has water of crystallization as is well known. Under the heating conditions during molding and film formation of a synthetic resin, a foaming phenomenon accompanying elimination of water of crystallization often occurs, and defective products may be given. Even if the zeolite is heat-treated to remove the so-called zeolite water to form an activated zeolite anhydrous, this water easily re-adsorbs. It was impossible to eliminate the effect.

Furthermore, when calcium carbonate used conventionally is used, since there is no crystallization water in calcium carbonate, there is no foaming phenomenon associated with the detachment of water of crystallization, but calcium carbonate originally has a strong cohesive force and primary Since secondary coarse particles in which a large number of particles are aggregated are easily formed, there is a problem to be improved as a blocking inhibitor for polyolefin films having both good blocking resistance and transparency.

[0005] In general, calcium carbonate, which is a raw material of limestone, is produced abundantly in Japan.
It is used in various fields as a filler for rubber and plastic. This calcium carbonate is generally heavy calcium carbonate and precipitated calcium carbonate (synthetic calcium carbonate)
Are roughly divided into two types.

[0006] Heavy calcium carbonate is a calcium carbonate prepared by mechanically pulverizing limestone and classifying the pulverized material to classify it into various grades, and has a feature that it can be produced relatively inexpensively. On the other hand, it is impossible to classify coarse particles and fine particles completely with the current classification technology, and as a result, calcium carbonate having a broad particle size distribution and a certain degree of fineness cannot be produced by the current pulverization classification technology. Therefore, it was not suitable as an anti-blocking agent for synthetic resin films such as polyolefin films.

On the other hand, as an industrial production method of synthetic calcium carbonate, a carbon dioxide gas method is widely adopted. In the carbon dioxide method, natural limestone is calcined to obtain quicklime (calcium oxide), and the quicklime is reacted with water to obtain lime milk (a suspension of calcium hydroxide in water). This is a method of obtaining calcium carbonate by conducting carbon dioxide gas generated when limestone is calcined and causing it to react. Synthetic calcium carbonate produced by this carbon dioxide method originally has a very strong cohesive force between primary particles,
A large number of primary particles aggregate to form large secondary particles (coarse aggregates of primary particles), and the slurry of the secondary particles is dispersed to almost the primary particles even if stirring is continued vigorously for a long time. That is said to be impossible. When synthetic calcium carbonate containing a large number of aggregates of such primary particles is used as a filler or pigment for various applications, secondary particles behave as if they were primary particles, poor dispersion, reduced strength, Good physical properties such as a decrease in gloss and a deterioration in fluidity cannot be obtained, and a compounding effect as in the case where primary particles are originally mixed cannot be obtained. Similarly, even if a synthetic calcium carbonate containing such a large number of aggregates is treated with an inorganic or organic surface treating agent, only the surface of the secondary particles is treated, and a sufficient effect is obtained. It doesn't work.

To date, there have been reported many methods for dispersing these primary particle aggregates.
A method of strongly pulverizing and breaking by a sand grinder mill or the like is employed. However, since such a method is grinding and pulverization using a large amount of energy, the aggregates are dispersed and the primary particles are destroyed at the same time, and as a result, the surface state is very unstable and desired. This is a preferable method because particles smaller than the primary particle diameter and secondary agglomerated particles with incomplete dispersion are mixed and the particle size distribution is widened. Also,
In a wet pulverizer such as a sand grinder, fine glass beads are usually used as a pulverizing medium.However, since the surface of these glass beads is also pulverized and destroyed during the pulverization and destruction step of calcium carbonate, A large number of coarse glass pieces of about 20 μm will be mixed in calcium, and for example, it is not possible to disperse and prepare calcium carbonate such as used as a filler for a thin film having a thickness of about 15 μm using such a wet grinding method. Not preferred. For the above reasons, conventional synthetic calcium carbonate was not sufficient as a blocking inhibitor for polyolefin films.

[0009]

SUMMARY OF THE INVENTION In view of the above facts, the present invention provides a polyolefin film having good blocking resistance and good transparency and not causing a foaming phenomenon in a film processing step or the like. It provides a composition.

[0010]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that a polyolefin composition using calcium carbonate having a specific particle size and a specific particle size as an anti-blocking agent. However, they found that they had the intended purpose, and completed the present invention.

That is, the present invention provides a polyolefin composition for a film, comprising calcium carbonate satisfying all of the following requirements (a) to (f). (A) 0.5 μm ≦ DS1 ≦ 10 μm (A) 0.25 μm ≦ DS2 ≦ 10 μm (C) DP3 / DS1 ≦ 1.25 (D) 1.0 ≦ DP2 / DP4 ≦ 2.5 (E) 1.0 ≤DP1 / DP5≤4.0 (f) (DP2-DP4) /DP3≤1.0, where DS1: average particle diameter (μm) of the major axis of primary particles examined by a scanning electron microscope (SEM) DS2: Average particle diameter (μm) of the short diameter of the primary particles examined by the above microscope DP1: Light transmission type particle size distribution analyzer (SA- manufactured by Shimadzu Corporation)
In the particle size distribution measured using CP3), the particle size (μ
m) DP2: In the particle size distribution measured using the above measuring device, the particle size (μm) at 25% of the cumulative weight calculated from the larger particle diameter side DP3: In the particle size distribution measured using the above measuring device, Particle size at 50% cumulative weight calculated from particle size side (μm) DP4: Particle size at 75% cumulative weight calculated from large particle size side (μm) DP5: In the particle size distribution measured using the above-mentioned measuring instrument, the content is a particle size (μm) at a cumulative weight of 90% calculated from the larger particle size side.

The measurement of the particle size by the light transmission type particle size distribution analyzer in the present invention is measured and calculated in the following manner. Measurement model: SA-CP3 manufactured by Shimadzu Corporation Measurement method: Solvent: ion-exchanged water and sodium polyacrylate 0.004
Preliminary dispersion: 100 seconds of ultrasonic dispersion Measured temperature: 27.5 ° C. ± 2.5 ° C. Measurement method: The following calculation example is used. DP1, 2, 3, calculated from the above particle size distribution measurement results
4 and 5 are as follows; DP1 = 2.00 + (11.0-10.0) x (3.00-2.00) ÷ (11.0-6.0) = 2.20 DP2 = 0.80 + (28.0-25.0) x (1.00-0.80) ÷ ( 28.0 -18.0) = 0.86 DP3 = 0.50 + (58.0 -50.0) x (0.60-0.50) ÷ (58.0 -42.0) = 0.55 DP4 = 0.30 + (82.0 -75.0) x (0.40-0.30) ÷ (82.0-72.0) = 0.37 DP5 = 0.15 + (94.0-90.0) x (0.20-0.15) ÷ (94.0-89.0) = 0.19 The DS of the present invention was measured using a scanning electron microscope manufactured by Hitachi, Ltd.

In the calcium carbonate which is an antiblocking agent used in the polyolefin composition for a film of the present invention, DS1 and DS2 are 0.5 μm ≦ DS1 ≦ 1
0 μm, 0.025 μm ≦ DS2 ≦ 10 μm, preferably 1 μm ≦ DS1 ≦ 5 μm, 0.5 μm ≦ DS2 ≦ 5 μ
m, which is arbitrarily selected depending on the type of polyolefin, the use and type of the film, and other required physical properties. When DS1 and DS2 exceed 10 μm, not only does the transparency of the film be impaired, but also a large number of coarse projections are present on the film surface, and the smoothness of the film surface is remarkably deteriorated, which is not preferable. DS1 is 0.
When it is less than 5 μm and DS2 is less than 0.25 μm, a film having sufficient blocking resistance cannot be obtained even when used in a large amount.

There is no particular limitation on the shape of calcium carbonate which is an anti-blocking agent used in the polyolefin composition for a film of the present invention. However, calcium carbonate having a flat plate-like structure generally has a sufficient blocking effect due to its shape effect. It is necessary to use a large amount of calcium carbonate in order to obtain the prevention effect, and the transparency and flexibility of the film or the like may be impaired. For DS1 / DS2 which is a function related to calcium carbonate, 1 ≦ DS1 / D
It is preferably in the range of S2 ≦ 3, more preferably 1
≤DS1 / DS2≤2, more preferably 1≤DS1 /
DS2 ≦ 1.5.

DP3 / DS1 and (DP2-DP4) / DP3 which are functions relating to the dispersion state of calcium carbonate
Is DP3 / DS1 ≦ 1.25, (DP2-DP4) /
DP3 ≦ 1.0, and DP3 / DS1 is 1.2
If it exceeds 5, and if (DP2-DP4) / DP3 exceeds 1.0, calcium carbonate will be constituted by a large number of secondary particles, and a film using such calcium carbonate as an antiblocking agent The size of the irregularities on the surface becomes uneven, and a film having sufficient blocking resistance cannot be obtained. In the field where higher blocking resistance is required, (DP
2-DP4) / DP3 is particularly preferably 0.5 or less.

The functions DP2 / DP4 and DP1 / DP5 relating to the particle size composition of calcium carbonate are 1.0 ≦ D
P2 / DP4 ≦ 2.5, 1.0 ≦ DP1 / DP5 ≦ 4.
0, and for applications requiring more advanced physical properties, 1.0 ≦ DP2 / DP4 ≦ 2.0, 1.0 ≦ DP1
It is preferred that /DP5≦3.0. DP2 / DP
4 exceeds 2.5, and DP1 / DP5 is 4.0
If it exceeds, the particle size distribution width of calcium carbonate becomes broad, the content of fine particles unnecessary for the anti-blocking ability and coarse particles causing coarse projections on the film surface increases, and sufficient blocking resistance and A film with good transparency cannot be obtained.

The crystal form of calcium carbonate used in the present invention is not particularly limited, and one of a hexagonal calcite crystal, an orthorhombic aragonite crystal, and a pseudo hexagonal vaterite crystal Alternatively, two or more kinds can be used, and cubic, spherical calcite-type calcium carbonate and spherical vaterite-type calcium carbonate are preferable from the viewpoint of uniformity of particle shape, dispersibility of particles, and the like.

Examples of the method for producing calcium carbonate that can be used in the present invention include a carbonate ion solution (for example, sodium carbonate) and a calcium solution (for example, calcium chloride) in which a reaction buffer (for example, sodium sulfate) for controlling the particle shape is dissolved. Are mixed, and a crystal growth terminator (eg, sodium hydroxide) is added during the reaction of the mixture to control the particle size, and by controlling the reaction conditions, a cubic calcite-type carbonate having an arbitrary particle size is obtained. It is possible to prepare calcium or spherical vaterite-type calcium carbonate. In addition, carbon dioxide gas is passed through a methanol suspension of quicklime or slaked lime containing a specific amount of quicklime or slaked lime and a specific amount of water to perform a carbonation reaction, and the temperature in the reaction system at a specific point in time during the carbonation reaction. Is adjusted to a specific temperature, and by specifying the time at which the conductivity in the reaction system reaches a specific value from the start of the carbonation reaction, spherical or elliptical spherical vaterite calcium carbonate having an arbitrary particle diameter is produced. It is possible.

However, the calcium carbonate for achieving the object of the present invention is not particularly limited to the above-mentioned production method, and any calcium carbonate satisfying the above requirements (A) to (F) can be used. Needless to say, it is not possible.

The calcium carbonate used in the present invention may contain organic acids such as fatty acids, resin acids, organic acids such as acrylic acid, oxalic acid and citric acid, tartaric acid, etc. in order to further improve the dispersibility and stability of the particles. Inorganic acids such as phosphoric acid, condensed phosphoric acid and hydrofluoric acid, surface treatment agents such as polymers thereof, salts thereof and esters thereof, dispersants such as surfactants, titanate coupling agents, silane coupling agents, etc. It is preferable to use the coupling agent or the like after surface treatment according to a conventional method.

The polyolefin constituting the polyolefin composition for a film of the present invention is not particularly limited as long as it is transparent and capable of forming a crystalline self-supporting film. Crystalline homopolymer of about 12 α-olefins, two or more crystalline copolymers, specifically, polyethylene, polypropylene, poly-4-methylpentene-1, ethylene-propylene random or block copolymer, Examples thereof include an ethylene-propylene-butene copolymer and an ethylene-propylene-hexene copolymer. Among them, polypropylene and propylene majority weight propylene and other α-
A polymer with an olefin is preferable, and a propylene polymer having an ethylene content of 0 to 6% by weight is particularly preferable. Further, these polyolefins are crystalline, and those having an isotactic index (II) of usually 40 or more, especially 60 or more, particularly 90 or more are suitable. Further, it is used as long as it can be molded, but usually has a melt flow rate (MFR) of 0.01 to 100 g / 10 min, especially 0.1 to 100 g / 10 min.
Those having 1 to 50 g / 10 min, particularly 0.5 to 10 g / 10 min are preferable.

The amount of the calcium carbonate blocking inhibitor used in such a polyolefin composition for a film is not uniform depending on the use of the film, the kind of the polyolefin resin, etc. 0.01 to 3 parts by weight is appropriate.
Preferred is 1 to 1 part by weight. The reason for this is that if the amount is less than the lower limit, the desired anti-blocking effect is insufficient due to the small amount of addition, and the precision of blending and uniformly dispersing in the polyolefin composition for a film is reduced. On the other hand, if it exceeds the upper limit, the transparency of the film is impaired, the block resistance is not improved for the added amount, and the stretchability of the film is undesirably reduced.

The polyolefin composition for a film of the present invention may contain other additives usually added to the polyolefin, such as pigments, dyes, ultraviolet absorbers, various stabilizers, antioxidants, light-shielding agents (eg, carbon black, titanium dioxide). Etc.), processing aids, and various additives such as an antistatic agent, and of course, if necessary, a blocking inhibitor other than calcium carbonate used in the present invention may be partially used in combination with the calcium carbonate of the present invention. . By stretching the polyolefin composition according to the present invention by a conventional method, a film having good workability, no foaming property, and excellent transparency and blocking resistance can be produced.

[0024]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, which do not limit the present invention.

Example 1 20 liters of 1.0 mol / l sodium carbonate aqueous solution and 0.2 mol / l sodium sulfate aqueous solution 2
While stirring 0 liter of the mixed solution in the reaction tank, 20 liters of 0.8 mol / liter calcium chloride aqueous solution was added thereto at a charging rate of 0.4 liter per second, and the carbonation reaction was performed with stirring. When the pH of the reaction system reached 11.0, sodium hydroxide was added so that the pH of the reaction system became 12.0, and then the mixture was stirred for 5 minutes to complete the reaction. The liquid temperatures before and after the reaction were 17.2 ° C and 17.0 ° C, respectively.
Was adjusted. Thereafter, dehydration was carried out in accordance with a conventional method, and the dehydrated cake was sufficiently washed with ion-exchanged water. Then, a surface treatment agent (sodium stearate) corresponding to 0.5% by weight of the obtained calcium carbonate was subjected to surface treatment under stirring. After drying, an anti-blocking agent composed of calcium carbonate powder was obtained. As a result of X-ray diffraction measurement, the obtained calcium carbonate powder was 100% vaterite-type calcium carbonate.
As a result of observation with M, it was cubic calcium carbonate having a particle size of 0.8 to 3 μm. Table 2 shows special values relating to the form, dispersity, and particle size of the calcium carbonate obtained in this example. Using the anti-blocking agent comprising calcium carbonate obtained in this example, a polypropylene composition was prepared in the manner described below to obtain a biaxially oriented polypropylene film, and the quality was evaluated. The results were as shown in Table 1.

Example 2 An anti-blocking agent composed of calcium carbonate powder was obtained in the same manner as in Example 1 except that the charging rate of the aqueous solution of calcium chloride was changed to 0.5 liter per second.
As a result of X-ray diffraction measurement,
It was 00% calcite-type calcium carbonate. As a result of observation by SEM, it was a cubic calcium carbonate having a particle diameter of 1 to 4 μm. Table 2 shows special values relating to the form, dispersity, and particle size of the calcium carbonate obtained in this example. Using the anti-blocking agent comprising calcium carbonate obtained in this example, a polypropylene composition was prepared in the manner described below to obtain a biaxially oriented polypropylene film, and the quality was evaluated. The results were as shown in Table 1.

Example 3 An anti-blocking agent composed of calcium carbonate powder was obtained in the same manner as in Example 1 except that the charging rate of the aqueous solution of calcium chloride was changed to 0.667 liter per second.

The obtained calcium carbonate powder was found to be 100% calcite-type calcium carbonate as a result of X-ray diffraction measurement, and was found to be cubic calcium carbonate having a particle diameter of 1 to 6 μm as observed by SEM. Table 2 shows special values relating to the form, degree of dispersion, and particle size of the calcium carbonate obtained in this example.
Shown in Using the anti-blocking agent comprising calcium carbonate obtained in this example, a polypropylene composition was prepared in the manner described below to obtain a biaxially oriented polypropylene film, and the quality was evaluated. The results were as shown in Table 1.

Example 4 20 liters of 0.7 mol / l sodium carbonate aqueous solution and 0.2 mol / l sodium sulfate aqueous solution 2
While stirring 0 liter of the mixed solution in the reaction vessel, 20 liters of a 0.53 mol / l aqueous solution of calcium chloride was added thereto at a charging rate of 0.33 liters per second, and the carbonation reaction was carried out with stirring. When the pH of the reaction system reached 10.7, sodium hydroxide was added so that the pH of the reaction system became 12.0, and then the mixture was stirred for 5 minutes to complete the reaction. The liquid temperatures before and after the reaction were 17.2 ° C. and 17.0 ° C., respectively.
Adjusted to ° C. Thereafter, the cake is sufficiently dehydrated according to a conventional method, and the dehydrated cake is sufficiently washed with ion-exchanged water. Then, a surface treatment agent (each weight ratio of acrylic acid and butyl methacrylate) corresponding to 1.5% by weight based on the obtained calcium carbonate is used. Is a 70:30 copolymer, in which 20% of the total carboxyl groups of the acrylic acid portion are ammonium salts), and the resulting mixture is subjected to surface treatment under stirring, followed by spray drying using a spray drier. An anti-blocking agent consisting of calcium carbonate powder was obtained. The obtained calcium carbonate powder is X
As a result of the line diffraction measurement, it was 88% vaterite-type calcium carbonate and 12% calcite-type calcium carbonate.
As a result of the observation, spherical calcium carbonate and cubic calcium carbonate having a particle diameter of 0.8 to 4 μm were obtained. Table 2 shows special values relating to the form, dispersity, and particle size of the calcium carbonate obtained in this example. Using the anti-blocking agent comprising calcium carbonate obtained in this example, a polypropylene composition was prepared in the manner described below to obtain a biaxially oriented polypropylene film, and the quality was evaluated. The results were as shown in Table 1.

Example 5 Granular quicklime having an activity of 82 (special grade reagent) was pulverized with a dry pulverizer (Coloplex; trade name, manufactured by Alpine).
The obtained quicklime powder was put into methanol, coarse particles were removed using a 200-mesh sieve, and a quicklime methanol suspension having a solid concentration of 20% as quicklime was prepared. The methanol suspension is wet-milled (Dynomill P
ILOT type; trade name, manufactured by WAB)
Methanol suspension dispersion D ₁ of the quicklime was prepared. The quicklime methanol added added to methanol suspension dispersion D _1, diluted to quicklime concentration of 3.0 wt%, further added 11 times equivalent moles of water to quicklime,
Methanol - quicklime - to prepare a mixed system M ₁ of water. 20
After adjusting the mixed system M ₁ containing quicklime 0g to 42 ° C., to conduct the carbon dioxide gas into the stirring conditions the mixed system was started carbonation reaction. 13 minutes after the start of the carbonation reaction, the supply of carbon dioxide gas was stopped when the pH in the system reached 10.0. The stirring in the system was continued even after the supply of carbon dioxide gas was stopped, and the stirring was stopped at a pH of 9.7 in the system 20 minutes after the start of the carbonation reaction. Got _two . Further, the mixing system M ₁ is collected containing quicklime 1600 g, methanol preform spherical vaterite type calcium carbonate described above - was dropped into aqueous suspension D _2, subjected to carbonation reaction allowed conducting carbon dioxide at the same time Was. Dropping rate of the mixed system M ₁ every minute as quicklime amount 0.833
g, temperature in carbonation reaction system is 41 ± 1 ℃, pH in carbonation system
Was controlled to 8.8 ± 0.1 to carry out the carbonation reaction, and the dropping carbonation reaction was terminated about 32 hours after the start of the dropping carbonation reaction.

In a mixed system of methanol, water and calcium carbonate prepared by the above method, a surface treating agent (weight ratio of each of acrylic acid and butyl methacrylate) corresponding to 1.5% by weight based on the obtained calcium carbonate was added. Is a 70:30 copolymer, in which 20% of the total carboxyl groups of the acrylic acid portion are ammonium salts), and the resulting mixture is subjected to surface treatment under stirring, followed by spray drying using a spray drier. An anti-blocking agent consisting of calcium carbonate powder was obtained.

The calcium carbonate prepared in this example was a spherical calcium carbonate having a 100% vaterite structure as a result of X-ray diffraction measurement. Table 2 shows special values relating to the form, dispersity, and particle size of the antiblocking agent obtained in this example. Using the anti-blocking agent comprising calcium carbonate obtained in this example, a polypropylene composition was prepared in the manner described below to obtain a biaxially oriented polypropylene film, and the quality was evaluated. The result is
As shown in Table 1.

Comparative Example 1 The concentration of calcium hydroxide prepared by adding water to slaked lime was 3
Milk casein was dissolved in calcium hydroxide in lime milk in an amount of 20% by weight, and the lime milk was adjusted to 3 ° C., and then 0% based on 1 mol of calcium hydroxide in lime milk. Carbon dioxide gas was passed at a conduction rate of 0.822 liters / minute to carry out carbonation reaction, and the carbonation reaction was completed at pH 6.5. After the carbonation reaction was completed, the mixture was allowed to stand for 24 hours, and then dehydrated by a conventional method. The obtained dehydrated cake was dried at 80 ° C. to obtain a blocking inhibitor composed of calcium carbonate powder.

As a result of X-ray diffraction measurement, the obtained calcium carbonate powder was 95% vaterite-type calcium carbonate. Table 3 shows special values relating to the form, the degree of dispersion, and the particle size of the antiblocking agent obtained in this comparative example. Using the anti-blocking agent composed of calcium carbonate obtained in this comparative example, a polypropylene composition was prepared in the manner described below, and a biaxially stretched polypropylene film was obtained, and its quality was evaluated. The results were as shown in Table 1.

Comparative Example 2 CO ₂ was added to 7.2 m ³ of lime milk at a temperature of 15 ° C. and a specific gravity of 1.070.
20% of furnace gas (hereinafter abbreviated as CO ₂ gas) having a concentration of 25%
The reaction was conducted at a flow rate of m ³ / min to complete the carbonation reaction. After the completion of the carbonation reaction, the temperature of the system was adjusted to 50 ± 5 ° C., the pH was adjusted to 10 ± 0.5 using CO ₂ gas and lime milk, and the mixture was stirred for 24 hours, and a viscous precipitated calcium carbonate aqueous solution having a viscosity of 2000 cps was obtained. A dispersion was obtained. 50 ± 5 ° C.該沈were prepared later made calcium carbonate aqueous dispersion (solid content concentration 14.9%) to 4m ³ milk of lime having a specific gravity of 1.070 was added dropwise at a rate of 0.6 m ³ / hr, at the same time CO ₂ The gas was passed, and the carbonation reaction was carried out at a system pH of 10 ± 0.5 with stirring. When the total amount of the lime milk drop reached 56 m ³ , the dropping of the lime milk was stopped, and the pH of the system was reduced to 7.0 until the pH reached 7.0.
O ₂ gas was passed through, and the obtained calcium carbonate was added at 0.1%.
A surface treatment agent (sodium stearate) corresponding to 5% by weight was subjected to surface treatment under stirring conditions, followed by dehydration and drying to obtain a calcium carbonate powder antiblocking agent.

The obtained calcium carbonate powder was 100% calcite-type calcium carbonate as a result of X-ray diffraction measurement, and was cubic calcium carbonate having a particle diameter of 0.8 to 3 μm as observed by SEM. Was. Table 3 shows special values relating to the form, degree of dispersion, and particle size of the calcium carbonate obtained in this comparative example. Using the anti-blocking agent composed of calcium carbonate obtained in this comparative example, a polypropylene composition was prepared in the manner described below, and a biaxially stretched polypropylene film was obtained, and its quality was evaluated. The results were as shown in Table 1.

Comparative Example 3 Heavy calcium carbonate (Super 1700: manufactured by Maruo Calcium Co., Ltd.) powder was suspended in warm water at 50 ° C. to obtain a calcium carbonate warm water suspension having a solid content of 15% by weight.
A surface treatment agent (sodium stearate) corresponding to 0.5% by weight of calcium carbonate was subjected to surface treatment under stirring, followed by dehydration and drying to obtain a blocking inhibitor composed of calcium carbonate powder.

The obtained calcium carbonate powder was 100% calcite-type calcium carbonate as a result of X-ray diffraction measurement, and was irregularly shaped calcium carbonate having a particle diameter of 0.3 to 9 μm as observed by SEM. Was. Table 3 shows special values relating to the form, degree of dispersion, and particle size of the calcium carbonate obtained in this comparative example. Using the anti-blocking agent composed of calcium carbonate obtained in this comparative example, a polypropylene composition was prepared in the manner described below, and a biaxially stretched polypropylene film was obtained, and its quality was evaluated. The results were as shown in Table 1.

The same methanol as used in Comparative Example 4 Example 4 - quicklime - to prepare a mixed system M ₁ of water. After adjusting the mixed system M ₁ containing quicklime 200g to 42 ° C., quicklime per mole of carbon dioxide gas into the stirring conditions the mixed system 0.082 mol / min
And the carbonation reaction was started. Five minutes after the start of the carbonation reaction, the conductivity in the system reached the maximum point, and the temperature in the system at the maximum point was adjusted to 45 ° C. Thereafter, the carbonation reaction was continued. When the electric conductivity in the system reached 100 μS / cm 19 minutes after the start of the carbonation reaction, the supply of carbon dioxide gas was stopped, and the carbonation reaction was stopped. In the mixed system of methanol, water and calcium carbonate prepared by the above method,
Surface treatment was performed in the same manner as in Example 4 to obtain a blocking inhibitor composed of calcium carbonate powder.

As a result of X-ray diffraction measurement, the calcium carbonate powder prepared according to this comparative example was an elliptic spherical calcium carbonate having a 100% vaterite structure. Table 3 shows special values relating to the form, the degree of dispersion, and the particle size of the antiblocking agent obtained in this comparative example. Using the anti-blocking agent composed of calcium carbonate obtained in this comparative example, a polypropylene composition was prepared in the manner described below to obtain a biaxially oriented polypropylene film, and the quality was evaluated. The results were as shown in Table 1. Example 1 above
In addition to the anti-blocking agents prepared according to Comparative Examples 1 and 4, a polypropylene composition was prepared in the following manner using A-type zeolite, kaolin clay, and synthetic silica, which are commercially available as anti-blocking agents for comparison. And
A biaxially stretched polypropylene film was obtained and its quality was evaluated. The results were as shown in Table 1.

Production of Film 100 parts by weight of a polypropylene resin having a melt flow rate of 1.9 g / 10 minutes, 0.10 parts by weight of 2,6-di-t-butyl-p-cresol as an antioxidant, Irganox 1010 (Product name, made by Ciba Geigy) 0.02
Parts by weight, 0.05 parts by weight of calcium stearate as a hydrochloric acid catching agent, and 0.08 parts by weight or 0.15 parts by weight of the antiblocking agent of the present invention were added, mixed with a super mixer, and then pelletized with an extruder. The pellets are formed into a sheet-like film using an extruder,
Stretched 5 times in the vertical direction and 10 times in the horizontal direction to finally achieve a thickness of 30
A μm stretched film was obtained. On one side of the stretched film,
Corona discharge treatment was performed. For these biaxially stretched films, transparency, blocking properties, and foaming properties were measured. Film transparency was measured by stacking four films in accordance with ASTM-D-1003. The blocking property of the films was set such that the contact area between the ^two films was 10 cm ² , placed between the two glass plates, and 50 g /
After leaving for 7 days in an atmosphere of 40 ° C. with a load of cm ² ,
Using a Shopper type testing machine, pulling speed 500mm /
And the maximum load was read and evaluated. The foamability of the film was determined by kneading 100 parts by weight of a resin (polyethylene (SMA-110)) with 1 part by weight of a mixed composition at 170 ° C. for 5 minutes with a roll.
A sample plate is obtained by press molding at 1 ° C. for 4 minutes to a thickness of 1 mm. The sample plate was sandwiched between glass plates as a sandwich layer, and left in a heating oven at 230 ° C. for 1 hour to observe a foaming state. The evaluation of the foaming property was visually evaluated according to the following criteria, and evaluated in four steps. 1: not foam at all like the blank 2: slightly foamed 3: considerably foamed 4: significantly foamed

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

As described above, the polyolefin composition for a film of the present invention exhibits good blocking resistance, provides a film having no foaming property and good transparency.

Claims (3)

(57) [Claims] 1. A polyolefin composition for a film, comprising calcium carbonate satisfying all of the following requirements (a) to (f): (A) 0.5 μm ≦ DS1 ≦ 10 μm (A) 0.25 μm ≦ DS2 ≦ 10 μm (C) DP3 / DS1 ≦ 1.25 (D) 1.0 ≦ DP2 / DP4 ≦ 2.5 (E) 1.0 ≤DP1 / DP5≤4.0 (f) (DP2-DP4) /DP3≤1.0, where DS1: average particle diameter (μm) of the major axis of primary particles examined by a scanning electron microscope (SEM) DS2: Average particle diameter (μm) of the short diameter of the primary particles examined by the above microscope DP1: Light transmission type particle size distribution analyzer (SA- manufactured by Shimadzu Corporation)
In the particle size distribution measured using CP3), the particle size (μ
m) DP2: In the particle size distribution measured using the above measuring device, the particle size (μm) at 25% of the cumulative weight calculated from the larger particle diameter side DP3: In the particle size distribution measured using the above measuring device, Particle size at 50% cumulative weight calculated from particle size side (μm) DP4: Particle size at 75% cumulative weight calculated from large particle size side (μm) DP5: particle size (μm) at a cumulative weight of 90% calculated from the larger particle size side in the particle size distribution measured using the above measuring instrument. 2. The composition according to claim 1, wherein DS1 / DS2 is calcium carbonate in the following range. 1 ≦ DS1 / DS2 ≦ 3 3. The composition according to claim 1, wherein the amount of the calcium carbonate is 0.01 to 3% by weight based on the polyolefin.