JPH05331300A - Polyester film - Google Patents

Abstract

PURPOSE:To provide a polyester film excellent in slippability and cut resistance, incorporated with alcoholic hydroxyl group-bearing silica particles prepared by reaction between an alkoxysilane compound and epoxy group-contg. silane compound. CONSTITUTION:Firstly, alcoholio hydroxyl group-bearing silica particles are synthesized by mixing (A) an alkoxysilane compound (e.g. tetraethoxysilane) with (B) an epoxy group-contg. silane compound (e.g. gamma- glycidoxypropyltrimethoxysilane) in ethanol followed by adding an aqueous HCl solution to the mixture to carry out reaction under agitation. Thence, the above silica particles are added to an ester interchange reaction product from dimethyl terephthalate and ethylene glycol followed by addition of a polycondensation catalyst such as antimony trioxide and then carrying out polycondensation at elevated temperatures under a high vacuum, and the resulting polyester is subjected to a melt extruder to produce a sheet, which is, in turn, put to biaxial drawing under heating and then heat set, thus obtaining the objective polyester film improved in slippability and cut resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film, and more specifically to a biaxially oriented polyester film having dispersed therein synthetic silica particles having an excellent affinity for polyester and having improved slipperiness and abrasion resistance.

[0002]

2. Description of the Related Art Polyester film represented by polyethylene terephthalate film is used in a wide variety of applications because of its excellent physical and chemical properties. For example, it is used for magnetic tapes, capacitors, photography, packaging, OHP.
It is used for applications.

In a polyester film, its slipperiness and abrasion resistance are major factors that affect the workability of the film manufacturing process and the processing process in each application, and the quality of the product. If these are insufficient, for example, when a magnetic layer is coated on the polyester film surface and is used as a magnetic tape, friction between the coating roll and the film surface during coating of the magnetic layer is severe, and the film surface is also greatly worn. In extreme cases, wrinkles, slip scratches, etc. on the film surface occur. Also, even after slitting the film after coating the magnetic layer and processing it into audio, video or computer tape, etc., when pulling out from the reel or cassette, winding up and other operations, many guide parts, playback heads etc. Abrasion occurs remarkably between them, and scratches and strains are generated, and a white powder substance is deposited due to abrasion of the surface of the polyester film, and as a result, it often becomes a major cause of loss of magnetic recording signals, that is, dropout.

Conventionally, as a method for lowering the friction coefficient of a polyester film, many methods in which fine particles are present in polyester have been proposed, but the affinity between the fine particles and polyester is not sufficient, and the transparency of the film is
Neither wear resistance was satisfactory. More specifically explaining this method, as means for improving the surface characteristics of polyester, a method of precipitating a part or all of a catalyst or the like used in polyester synthesis in the reaction process (internal particle precipitation method) Many methods have been proposed for adding fine particles such as calcium and silicon oxide during or after polymerization (external particle addition method).

However, the internal particle deposition method of
Since the particles are a metal salt of the polyester component, etc., the affinity with polyester is somewhat good, but since it is a method of generating particles during the reaction, it controls the amount of particles, particle size, and prevents the formation of coarse particles. Is difficult.

On the other hand, the external particle addition method is excellent in terms of slipperiness by appropriately selecting the particle size, the addition amount, and the like, and adding fine particles obtained by removing coarse particles by classification or the like. However, since the affinity between the inorganic fine particles and the polyester, which is the organic component, is not sufficient, peeling occurs at the interface between the particles and the polyester during stretching, and voids are generated.

When the voids are present in the polyester film, the particles are easily separated from the polyester film due to damage of the polyester film or the like due to contact between the polyester films or between the polyester film and another substrate. This may cause white powder and dropouts on the tape film. Also, since there are large voids around the particles, the transparency of the polyester film is impaired. Therefore, the lack of affinity between the inorganic particles and polyester is a problem to be solved in terms of abrasion resistance and transparency.

Among the inorganic particles, silica (silicon oxide)
Shows basically good characteristics, but some proposals have been made in response to high quality requirements in recent years. For example, a surface treatment by a coupling reaction with a silane compound or a titanate compound as disclosed in JP-A-57-18738 and 57-76036, and JP-A-63-280.
Surface treatment by a graft reaction with a glycol component such as No. 763 can be mentioned, but there is a problem that the effect is not as expected.

[0009]

In view of the above-mentioned circumstances, the present inventors are excellent in slipperiness and abrasion resistance, and are also excellent in the shape, size, distribution, etc. of film surface protrusions, and are suitable for various applications. As a result of diligent studies to obtain a biaxially oriented polyester film having the above characteristics, a polyester film containing silica synthesized by using a compound capable of forming an alcoholic hydroxyl group component is not peeled at the interface between particles and polyester. They have found that they have improved and have good properties and have arrived at the present invention.

Accordingly, it is an object of the present invention to provide a biaxially oriented polyester film having small voids and excellent in slipperiness and abrasion resistance.

[0011]

Means for Solving the Problems That is, the present invention is to disperse and contain silica particles having an alcoholic hydroxyl group, which are synthesized by the reaction of an alkoxysilane compound and a silane compound having an epoxy group, in a polyester film. It is a characteristic polyester film.

The polyester in the present invention is a polyester having an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. Such polyesters are substantially linear and have film-forming properties, especially film-forming by melt molding.

Examples of the aromatic dicarboxylic acid include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenylethanedicarboxylic acid, biphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylketonedicarboxylic acid and anthracene. Dicarboxylic acid etc. can be mentioned.

Examples of the aliphatic glycol include polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and decamethylene glycol, and cyclohexanedimethanol. Such alicyclic diols and the like can be mentioned.

In the present invention, the polyester having alkylene terephthalate and / or alkylene naphthalate as a main constituent is preferable as the polyester.

Among such polyesters, especially polyethylene terephthalate and polyethylene-2,6-naphthalate, for example, 80 mol% or more of the total dicarboxylic acid component is terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, A copolymer in which 80 mol% or more of all glycol components is ethylene glycol is preferable. 20 mol% or less of the total acid component can be the above aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid can be used. Acids; can be alicyclic dicarboxylic acids such as cyclohexane-1,4-dicarboxylic acid and the like. Further, 20 mol% or less of the total glycol component may be the above-mentioned glycol other than ethylene glycol, and aromatic diols such as hydroquinone, resorcin, and 2,2-bis (4-hydroxyphenyl) propane; 1 Aliphatic diol having aromatic ring such as 4-dihydroxymethylbenzene; Polyalkylene glycol (polyoxyalkylene glycol) such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol
And so on.

The polyester of the present invention includes
Aromatic oxy acids such as hydroxybenzoic acid; ω-
Those in which a component derived from an oxycarboxylic acid such as an aliphatic oxyacid such as hydroxycaproic acid is copolymerized or bonded at 20 mol% or less based on the total amount of the dicarboxylic acid component and the oxycarboxylic acid component are also included.

Further, in the polyester of the present invention, a polycarboxylic acid or polyhydroxy compound having a functionality of 3 or more, such as trimellitate, can be used in an amount in a substantially linear range, for example, an amount of 2 mol% or less based on the total acid component. Also included are those obtained by copolymerizing acid, pentaerythritol and the like.

Further, in the polyester of the present invention,
Other additives such as pigments, dyes, ultraviolet absorbers, heat stabilizers, light stabilizers, antioxidants, light-shielding agents (eg, carbon black, titanium dioxide, etc.) can be contained as necessary.

The silica particles in the present invention are silica particles having an alcoholic hydroxyl group in the particles or on the surface of the particles, which are synthesized by a polycondensation reaction of an alkoxysilane compound and a silane compound having an epoxy group. Specific examples thereof include silica particles synthesized by polycondensation of tetraethoxysilane and γ-dilysidoxypropyltrimethoxysilane.

The silane compound having an epoxy group is not particularly limited as long as it has an epoxy group in the molecule, and the alkoxysilane compound is not particularly limited as long as it has an alkoxy group such as methoxyethoxy and butoxy.

The silica particles in the present invention preferably have a volume shape factor defined by the following formula in the range of 0.36 to π / 6.

[0023]

[Equation 1]

Further, the ratio of major axis to minor axis of silica particles (major axis /
A true spherical or rugby ball-shaped particle having a (minor diameter) of 1.0 to 2.5 is preferable from the viewpoint of film running property and abrasion resistance.

The average diameter of the silica particles is 0.1-5.
μm is preferable, and 0.2 to 2 μm is more preferable. From the viewpoint of sharpening the distribution of protrusions on the film surface, the relative standard deviation of the particle size defined below is preferably 0.7 or less, more preferably 0.5 or less.

[0026]

[Equation 2]

In the present invention, the content of the silica particles is different from that of polyester in terms of running property of the film and cost.
0.005 to 5% by weight is preferable, 0.01 to 3% by weight
Is more preferable.

The silica particles in the present invention are preferably subjected to a coarse particle removal process by a refining process before being incorporated into polyester. Examples of the classification means include a wet or dry centrifuge, filter filtration and the like. These means may be used in combination of two or more kinds and may be purified stepwise.

The silica particles may be added to the polyester at any time and by any method, but it is preferable to add them as a glycol slurry before the polymerization reaction of the polyester reaction, particularly before the completion of transesterification or esterification reaction. ..

The polyester film can be obtained by forming the above polyester as it is or by diluting it with another polyester (polyester not containing silica particles in a predetermined ratio) to form a film. Other polyesters used for dilution include, for example, polyester produced by a conventional precipitation method or addition method or a polyester containing no particles.

The polyester film of the present invention preferably has a concave and convex unit formed on the surface of the film by projections derived from silica particles and depressions adjacent to the projections, from the viewpoint of slipperiness and abrasion resistance of the film.

This unevenness unit is not the unevenness formed by a conventional mechanical stamp such as embossing, but is generated by the deformation of the film itself in the process of stretching the film. Stretching conditions can be mentioned.

In uniaxially stretching the unstretched film of polyester containing silica particles in the machine axial direction (longitudinal direction of the film), the stretching temperature is set to a high temperature or (and) the stretching ratio is set to a low value, and then By performing the second axial stretching (stretching in the width direction of the film), it is possible to form the protrusions caused by the particles and the depressions adjacent to the protrusions.

In the stretching of the film, it is stretched in the usual machine axial direction (first axial direction) and width direction (second axial direction), and then further stretched in the first axial stretching direction and / or the second axial stretching direction. It is also possible to perform high-stage (multi-stage) stretching in which Also in this case, the effect of the present invention is maintained because the shape of the unevenness unit formed by the projections and depressions on the film surface is slightly deformed and still exists.

Since the polyester film of the present invention has projections and projections formed by silica particles, and in some cases, projections and depressions formed by the projections and the depressions adjacent to the projections, the polyester film of the present invention can be brought into contact with other films or equipment that comes into contact with the film. The area can be reduced, the surface is flat, and the sliding effect and wear resistance are excellent. Further, it has an advantage that the abrasion resistance is enhanced as compared with the conventional polyester film in which the surface of the film has projections formed by simple particles.

Incidentally, as long as the effect of the present invention is not impaired, it is caused by externally added particles which are insoluble in polyester and have an ordinary shape such as a lump or plate, and / or internally precipitated particles which are precipitated during the synthesis of polyester. There is no problem even if the projections and projections and the concavo-convex units having the depressions having the particles as the core are mixed on the surface of the polyester film.

The polyester film of the present invention has various advantages such as a flat surface, excellent slipperiness, and good abrasion resistance as compared with conventional polyester films, and thus can be used for various applications. In particular, it can be preferably used in the magnetic tape field and the like where abrasion resistance is required.

[0038]

EXAMPLES The present invention will be described in more detail below with reference to examples. In addition, "parts" in the examples means parts by weight, and each characteristic value was measured according to the following methods.

(1) Particle Diameter The particle diameter can be measured in the following states.

1) To obtain the average particle size, particle size ratio, etc. from the powder 2) To obtain the average particle size, particle size ratio, etc. of the particles in the film 1) From the powder On the electron microscope sample stand The powder is dispersed so that the individual particles do not overlap as much as possible, a gold thin film deposition layer is formed on this surface with a thickness of 200 to 300 angstroms by a gold sputtering device, and, for example, 10,000 to 3 with a scanning electron microscope.
Observing at a magnification of 10,000, a major axis (Dli), a minor axis (Dsi) and an area circle equivalent (Di) of at least 100 particles are determined with Luzex 500 manufactured by Nippon Regulator Co., Ltd. Then, the average particle size is calculated from these values.

2) Particles in film A small piece of sample film was fixed on a sample stand for a scanning electron microscope, and was sputtered by JEOL Ltd. (JFC-
The film surface is subjected to ion etching treatment under the following conditions using a 1100 type ion etching apparatus). The condition is that the sample is placed in a bell jar, the degree of vacuum is raised to a vacuum state of about 10 ^-3 Torr, the voltage is 0.25 KV, and the current is 1
Ion etching is performed at 2.5 mA for about 10 minutes. Further, gold sputtering is applied to the film surface with the same apparatus, and 10,000 to 30,000 is observed with a scanning electron microscope.
Observed at double magnification, and use Luzex 500 manufactured by Nippon Regulator Co., Ltd. to obtain at least 100 particles with a long diameter (Dli),
The minor axis (Dsi) and the area equivalent circle diameter (Di) are obtained. Then, the average particle size is calculated from these values.

(2) Affinity The periphery of particles in the film (surface) is exposed according to the method of (1) -2) above, and the major axis of at least 50 fine particles and the major axis of voids are measured. The number average value of the void ratio represented by the major axis of voids / the major axis of particles is calculated.

This number average value is displayed according to the following judgment criteria. 1st class: 1 ≤ void ratio <1.5 (that is, no voids or very small) 2nd class: 1.5 ≤ void ratio <2.0 3rd class: 2.0 ≤ void ratio <3.0

(3) Scrapability Scrapability of the running surface of the film is evaluated using a 5-stage mini super calendar. The calender is a five-stage calender of nylon roll and steel roll, the processing temperature is 80 ° C., the linear pressure applied to the film is 200 kg / cm, and the film running speed is 50 m / min. 1 full length film
At the time when the film has been run for 10,000 m, the abrasion of the film is evaluated by the dirt attached to the top roller of the calendar. <Four-level judgment> ◎ Nylon roll is not soiled at all ○ Nylon roll is barely soiled × Nylon roll is soiled × × Nylon roll is heavily soiled

[0045]

Example 1 [Synthesis of silica] tetraethoxysilane (TEOS) 8
1 part, 15 parts of γ-glycidoxypropyltrimethoxysilane (γ-GPS) and 100 parts of ethanol were charged into a reaction vessel and stirred. Next, 1000 parts of a hydrochloric acid aqueous solution was added and the reaction was carried out under stirring.

The average particle size of the obtained silica particles having an alcoholic hydroxyl group was 0.8 μm. [Synthesis of polyester and production of film] 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol,
After transesterification according to a conventional method using 0.035 part of manganese acetate tetrahydrate as a catalyst, trimethyl phosphate of 0.1.
03 parts was added, and the alcoholic hydroxyl group-containing silica obtained above was further added with stirring so as to be 0.2% by weight with respect to the polyester.

Thereafter, 0.03 part of antimony trioxide was added, and the polycondensation reaction was carried out in the usual manner under high temperature and high vacuum,
Intrinsic viscosity number (Orthochlorophenol, 35 ° C) 0.6
0 dl / g of polyethylene terephthalate was obtained.

Next, the obtained polyethylene terephthalate was dried at 180 ° C., formed into a sheet by a melt extruder, and then biaxially stretched at 90 ° C. to a longitudinal stretching ratio of 3.5 times and a transverse stretching ratio of 4.0 times. Then heat set, thickness 15μm
It was a film.

The characteristics of this film are shown in Table 1. Mostly, there is no void around silica in the obtained film,
Even if it was, it was extremely small. The film was also excellent in abrasion resistance and transparency.

[0050]

Example 2 60 parts of TEOS in the synthesis of silica,
A film was obtained in the same manner as in Example 1 except that 35 parts of γ-GPS was used.

The characteristics of the film are shown in Table 1 and were good.

[0052]

Comparative Example 1 A film was obtained in the same manner as in Example 1 except that only 90 parts of TEOS was used in the synthesis of silica.

The characteristics of the film are shown in Table 1, but the abrasion resistance was insufficient.

[0054]

[Table 1]

[0055]

EFFECTS OF THE INVENTION According to the present invention, synthetic silica particles having an excellent affinity for polyester are dispersedly contained, and slipperiness,
A biaxially oriented polyester film with improved abrasion resistance can be provided.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C08L 83:02) 8319-4J B29K 67:00 B29L 7:00 4F

Claims (5)

[Claims] 1. A polyester film in which silica particles having an alcoholic hydroxyl group, which are synthesized by a reaction of an alkoxysilane compound and a silane compound having an epoxy group, are dispersedly contained in the polyester film. 2. The average particle size of silica particles is 0.05 to 5 μm.
2. The polyester film according to claim 1, wherein the content of silica particles is 0.005 to 5% by weight based on the polyester. 3. The alkoxysilane compound is tetramethoxysilane, and the silane compound having an epoxy group is γ.
-The polyester film according to claim 1, which is glycidoethoxypropyltrimethoxysilane. 4. The polyester film according to claim 1, wherein the silica particles are substantially spherical. 5. The polyester film according to claim 1, wherein the polyester film is a biaxially oriented polyethylene terephthalate film or a biaxially oriented polyethylene-2,6-naphthalate film.