JPS62252452A - Polyamide film - Google Patents

Abstract

PURPOSE:To contemplate well-balanced improvements in slipperiness, surface gloss and transparency of a polyamide film, by dispersing wet-process amorphous silicon dioxide having specified physical properties in a polyamide. CONSTITUTION:A polyamide film is obtd. from a blend obtd. by dispersing 0.05-1.0pt.wt. wet-process amorphous silicon dioxide (A) having an average particle size of 0.1-6mu, a specific surface area of 50-300m<2>/g and a sodium content (in terms of Na2O) of 0.1-1.0% as measured by flame analysis in 100pts. wt. polyamide (B). Any of conventional polyamides such as nylon 6, nylon 6,6, etc., can be used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a polyamide film, and more particularly to a polyamide film having good slipperiness, surface gloss, and transparency in a well-balanced manner.

(Prior Art) Polyamide films are widely used mainly in the field of food packaging because they have excellent properties such as transparency, pinhole resistance, oxygen gas barrier properties, heat resistance, and oil resistance. This film is divided into stretched film and unstretched film.

In general, polyamide films have poor slip properties, and this tendency becomes particularly noticeable under high humidity conditions due to polyamide's water absorption properties. Poor slipperiness causes trouble not only during film formation or winding, but also during post-processing such as lamination or printing, so there has been a strong desire for polyamide films to have improved slipperiness.

To improve this slipperiness, metal soaps, bisamides,
Although it is known to add polyolefins or various inorganic particles, it is particularly effective to incorporate inert inorganic particles such as silicon dioxide, talc, and kaolin. The slipperiness of this film is controlled by the surface structure of the film, and in systems containing inorganic particles, the slipperiness increases in proportion to the size and amount of surface protrusions caused by the inorganic particles, but at the same time, these surface protrusions cause the surface gloss of the film. is lost. In other words, in order to sufficiently improve the slipperiness of the film, it is necessary to increase the amount of inorganic particles added, and as a result, the transparency and surface gloss of the film are impaired, and the commercial value for packaging is lost. Particularly in the case of stretched polyamide films, surface gloss is important, so a reduction in surface gloss and a resulting reduction in commercial value are a major problem.

Conventionally, polyamide compositions for film forming aimed at such improvements include (1) a composition comprising polyamide, an α,β-unsaturated carboxylic acid-olefin copolymer, and inorganic particles (Japanese Unexamined Patent Publication No. 52-32945; (see Japanese Patent Publication No. 51-2830
(Refer to Publication No. 7), ■ Polyamide, talc that does not substantially contain particles with a particle size of top or more, and HLB of 10 to 1
A composition consisting of a nonionic surfactant having a range of
(see Japanese Patent Publication No. 57-4741) have been proposed.

(Problems to be Solved by the Invention) However, these techniques are not practical, especially for polyamide films that are extremely thin and require high levels of slipperiness and transparency, such as biaxially oriented polyamide films. Moreover, the improvement effect is not sufficient.

Furthermore, in order to simultaneously improve the physical properties of transparency and slipperiness, which are incompatible, it is important to select the type, particle size, shape, etc. of the inorganic particles to be added, as well as the method of dispersing them. However, sufficient studies have not yet been made on polyamide films, which have poor slip properties.

[Structure of the Invention] (Means for Solving the Problems) As a result of extensive research in order to solve the above-mentioned problems, the present inventors have found a method that has a predetermined average particle size, specific surface area, and sodium content. We discovered that by dispersing a specific amount of amorphous silicon dioxide synthesized by a predetermined method in polyamide, a polyamide film having a good balance of slipperiness, surface gloss, and transparency can be obtained, and we have developed this book. He has completed his invention.

That is, the polyamide film of the present invention contains (A) polyamide in 100 parts by weight.

(B) have an average particle size of 0.1 to 6 µl, and 50 to 30 µl;
It has a specific surface area of 0 m''/g, and the content of sodium (Na) by flame spectroscopy is higher than that of sodium oxide (N
0.1 to 1.0% in terms of a2O), and 0.05 to 1.0 parts by weight of amorphous silicon dioxide synthesized by a wet method is dispersed therein.

Any polyamide as component (A) used in the present invention may be used, such as 6-nylon, 6.6-nylon, 11-nylon, 12-nylon, 6. lO-Nylon, 6.11 ~ Nylon, 6.12
- Nylon, poly(methaxylylene adipamide), poly(para-xylylene adipamide). These polyamides may be blends, such as 6-nylon/6,6-nylon, 6-nylon/12-nylon, 6-nylon/6,10-nylon, 6-nylon 76T-nylon (T: terephthalic acid Copolymers such as 6-nylon/6, 6-+ylon/12-nylon, and 6-nylon/6,6-nylon/6,10-nylon can also be used.

Silicon dioxide, which is the component CB) used in the present invention, is
Average particle size, specific surface area (hydroxyl group concentration on particle surface), and N
The amorphous silicon dioxide is synthesized by the predetermined method described above with the a content within the predetermined range described above.

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If it is less than 6#L, the slipperiness will not be improved much, and if it exceeds 6#L, large protrusions will appear on the film surface and the surface glossiness of the film will deteriorate. The preferred average particle size of amorphous silicon dioxide is 0.5 to 6 microns. Note that for thin stretched films with a thickness of 15 mm or less, consideration should be given to the classification and dispersion method so as not to substantially contain particles of 10p or more in order to prevent the film from breaking during stretching.

If the specific surface area is less than 50 m''/g, the affinity with polyamide will decrease and the transparency of the film will also decrease.
If it exceeds G/g, the hydroxyl groups on the particle surface will strongly bond, reducing the dispersibility of each particle and impairing the transparency of the film.
Preferably it is 100-200rrf/g.

If the sodium content is less than 0.1%, the cohesive force between particles will be large, making dispersion Φ classification difficult, and if it exceeds 1.0%, the desired effect will not be obtained, preferably from 0.2 to
It is 0.6%.

Generally, the methods for synthesizing amorphous silicon dioxide include dry method,
Examples include a wet method and a silicic acid gelling method, but the effects of the present invention can be obtained only when amorphous silicon dioxide synthesized by applying a wet method is used. In the case of this wet method, silicate is decomposed with acid to synthesize it. When using the dry method or the gelation method, the Na content determined by the flame analysis method is N
While the content is less than 0.1% in terms of a2O, in the case of the wet method, it is contained in an amount of 0.1% or more in terms of Na2O.

If the blending ratio of component (B) is less than 0.05 parts by weight, slipperiness will be insufficient, and if it exceeds 1.0 parts by weight, transparency will decrease. Preferably it is 0.1 to 0.5 part by weight.

Furthermore, a coloring agent, an antioxidant, a heat stabilizer, a weather resistance imparting agent, an antistatic agent, etc. may be added as necessary.

Next, the method for manufacturing the polyamide film of the present invention will be explained.

First, a mixture consisting of the components (A) and (B) described above is obtained, and then a conventional film forming method is applied to the obtained mixture to easily produce the film.

In the step of obtaining the above-mentioned first-stage mixture, the above-mentioned (
Component B) can be added at any stage of polyamide molded product production, for example, it may be added to the polyamide raw material before one polymerization, or it may be added at any time after the start of the polymerization reaction. .

Furthermore, after the polymerization reaction is completed and before being formed into pellets.

Alternatively, it can be added to the polyamide during molding or after pelletization. When adding component (B) to the raw material before polymerization, for example, when producing 6-nylon using ε-caprolactam as a raw material and using water as a catalyst, component (B) is first added to water or 50 to 80% by weight. (-It is preferable to add the component after dispersing it in the caprolactam aqueous solution because it will be uniformly blended into the raw material, and the CB) component is 1.0% by weight.
A polyamide composition containing the above-mentioned high concentration is prepared in advance, and this and a polyamide containing no component (B) are appropriately mixed before being formed into a film, and finally the polyamide (
Component B) may be contained in an amount of O, OS to 1.0% by weight.

In the step of obtaining the film in the latter stage described above, the obtained mixture is extruded from an extruder at an extrusion temperature of 220 to 300°C, and cooling is performed on the casting roll surface in the case of the casting method (T-die method). Alternatively, in the case of the tubular method, various multilayer films may be formed by air cooling or water cooling, or by coextrusion with polyolefin or the like. Furthermore, in the case of a stretched film, an unstretched film formed by a casting method or a tubular method is meraxially or biaxially stretched at a stretching temperature of 50 to 180°C, and if necessary, at a stretching temperature of 120°C or higher.
It is common to heat set at a temperature 10°C lower than the melting point. In the case of biaxial stretching, a known method such as a tenter two-vehicle stretching method or a tubular biaxial stretching method may be applied.

The polyamide film of the present invention has a good balance of slipperiness, surface gloss, and transparency, and is therefore extremely useful for applications such as food packaging.

In the following, the wood invention will be explained in more detail with reference to Examples and Comparative Examples. In addition, in the examples, the physical properties of the inorganic particles were measured according to the following method.

Three units and one: By microscopy. After photographing a polyamide film containing inorganic particles between cover glasses, the maximum particle size of each particle was measured, and the average particle size was calculated.

! IJi! i: A value calculated using the BET adsorption theoretical formula after adsorbing nitrogen gas was used.

Hanshu, Danji 1: Measurements were made by flame spectroscopy on silicon dioxide dried at 110°C for 2 hours.

(Example) Amorphous silicon dioxide (average particle size 2.8
specific surface area 140 m''/g, Na2O content 0.3%
) fine powder dispersed in an aqueous Q-caprolactam solution was added to melted (-caprolactam) and polymerized in a conventional manner to obtain 6-nylon with a silicon dioxide content of 1.2% by weight. 5 parts by weight of silicon dioxide-free 6-nylon pellets were blended with 1 part by weight of pellets, and the amount of silicon dioxide added was 0.2% by weight.

The blended 6-nylon pellets were melt-extruded from a T-die at 250°C using an extruder and extruded onto a cooling roll at 40°C to obtain an unstretched film with a thickness of 140IL. The film was simultaneously biaxially stretched at a stretching temperature of 120° C. and a stretching ratio of 3.0 times in the longitudinal and lateral directions, and heat-set at 190° C. to obtain a two-wheel stretched film with a thickness of 15 tiles.

The transparency and slipperiness of the obtained film were evaluated as follows. The results are also shown in Table 1.

Wataru Iromame = Using a slip tester made by Nippon Rigaku Kogyo,
The coefficient of static friction (S) was measured in accordance with ASTM 01894-63 at 23° C. and in an atmosphere of 65% relative humidity.

115: Using a direct reading haze meter manufactured by Suga Test Instruments,
The seismic intensity (baize) of the film was measured according to ASTM D-1003, and the surface glossiness (gloss) of the film was measured according to ASTM D-523 using a digital variable angle gloss meter manufactured by Suga Test Instruments.

A film was formed and stretched in the same manner as in Example 1, except that the blend ratio was changed and the amount of silicon dioxide added was 0.5% by weight and 0.09% by weight. The results are shown in Table 1.

Amorphous silicon dioxide synthesized by wet method (average particle size 2.0
．． , specific surface area 250rrf/g, Na2O content 0.5
%) was polymerized in the same manner as in Example 1 (silicon dioxide content: 0.2% by weight), and film formation and stretching were performed in the same manner as in Example 1 using this pellet. The results are shown in Table 1.

Xmu1J Amorphous silicon dioxide synthesized by wet method (average particle size 0.7
g, specific surface area 80 m''/g, Na2O content 0.2%)
was polymerized in the same manner as in Example 1 (silicon dioxide content: 0.3% by weight), and film formation and stretching were performed in the same manner as in Example 1 using this pellet. The results are shown in Table 1.

Comparison ±Uni” Polymerization was carried out in the same manner as in Example 1 using amorphous silicon dioxide synthesized by a wet method and having different average particle diameters and specific surface areas. Using this pellet, film formation and stretching were performed in the same manner as in Example 1. The results are shown in Table 1.

When the average particle size is very small as 0.051L, the slipperiness is insufficient (Comparative Example 1), when the specific surface area is as small as 40 m'/g, the transparency deteriorates (Comparative Example 2), and conversely, when the specific surface area is 4.
If it is as large as 00 m''/g, the dispersibility of silicon dioxide becomes poor and transparency is impaired (Comparative Example 3). Even if the average particle size and specific surface area are within this range, the amount added is 1.2% by weight. When the amount is too high, the transparency deteriorates (Comparative Example 4), and on the other hand, when it is 0.0
When it is as low as 4% by weight, slipperiness deteriorates (Comparative Example 5)
.

Tsutsumi Mojo J Aerosil (AERO9IL) 2O synthesized by dry method
0 (trade name, manufactured by Nippon Aerosil ■, average particle size 3:2g,
Specific surface area 2O0ni”/gt Na2O content 0.
1% or less) and polymerized in the same manner as in Example 1 (silicon dioxide content: 0.3% by weight). Using this pellet, film formation and stretching were performed in the same manner as in Example 1. The results are shown in Table 1.

In this example, silica was poorly dispersed and transparency was poor.

Comparison 11 Thyroid 244 synthesized by gelation method (trade name, manufactured by Fuji Davison Chemical ■, average particle size 3.5, specific surface area 300
rn'/g, Na2O content 0.06-0.1
%), polymerized in the same manner as in Example 1 (silicon dioxide content: 0.3% by weight), and using this pellet, film formation and Φ stretching were performed in the same manner as in Example 1. The results are shown in Table 1.

In this example, the film surface was severely uneven, resulting in poor gloss and transparency.

Lukasa 1'' was polymerized in the same manner as in Example 1 using talc with an average particle size of 1.6 IL (talc content: 0.3% by weight), and film formation and stretching were performed in the same manner as in Example 1 using this pellet. The results shown in Table 1 were obtained.

In this example, since talc has a nucleating effect, crystallization progressed and transparency deteriorated.

Comparative Example J Using kaolin with an average particle size of O, a = polymerized in the same manner as in Example 1 (kaolin content 0.2%), film formation and stretching were performed in the same manner as in Example 1 using this pellet. and the first
Obtained the results in the table.

In this example, since the film surface was highly uneven, the slipperiness was good, but the surface gloss was very poor.

Fruit” 01j 6-Nylon powder (particle size 300 mesh or less) 85
Parts by weight, 10 parts by weight of silicon dioxide synthesized by the wet method used in Example 1, and 5 parts by weight of ethylene bisstearylamide as a dispersant were blended in a Henschel mixer. The obtained blended product was mixed with a twin-screw extruder for 26 hours.
The mixture was kneaded and extruded at 0°C to obtain master pellets having a silicon dioxide content of 10% by weight. 3 parts by weight of this master pellet and 97 parts by weight of 6-nylon pellets containing no silicon dioxide were blended, and the amount of silicon dioxide added was 0.3% by weight.

Using this pellet, it was extruded through a T-die at 250°C using an extruder and solidified on a cooling roll at 80°C to form a film with a thickness of 50 l. The results are shown in Table 2.

In this example, a film with good transparency and slipperiness was obtained.

Comparison m Comparative Example 6 (7) A master pellet was prepared in the same manner as in Example 6 except that AERO9IL 2O0 (synthesized by dry method) was used, and then film molding was performed (silicon dioxide addition amount: 0.3% by weight) ), the results are shown in Table 2.

In this example, fish eyes were generated due to poor dispersibility of silicon dioxide, resulting in very poor transparency.

A master pellet was prepared in the same manner as in Example 6, except that Thyroid 244 of Comparative Example 7 (synthesized by a gelling method) was used, and then film molding was performed (silicon dioxide addition amount was 0).
．． 3% by weight), the results are shown in Table 2.

In this example, the dispersion of silicon dioxide was still poor, fish eyes were generated, and the transparency was deteriorated.

[Effects of the Invention] As detailed above, the polyamide film of the present invention has good slipperiness, surface gloss, and transparency in a well-balanced manner, and therefore is useful for food packaging, for example. The practical value is extremely large.

Claims (1)

Scope of Claims: (A) in 100 parts by weight of polyamide, (B) having an average particle size of 0.1 to 6μ, and 50 to 30μ
It has a specific surface area of 0 m^2/g, and the sodium content measured by flame spectroscopy is 0.1 to 1 in terms of sodium oxide (Na_2O).
．． A polyamide film comprising 0.05 to 1.0 parts by weight of amorphous silicon dioxide synthesized by a wet method.