KR100215481B1 - Polyester film - Google Patents

Abstract

The present invention relates to a polyester comprising 0.01 to 2.0 parts by weight of needle-shaped particles insoluble in polyester and 0.01 to 3.0 parts by weight of a plate-like particle insoluble in polyester, based on the total weight of the polyester, Lt; / RTI > The polyester film according to the present invention not only improves lubricity and abrasion resistance by containing a predetermined amount of needle-shaped or plate-shaped particles whose needle bed ratio and average particle size are controlled, but also has good slitting property at the time of processing into a magnetic tape, There is an advantage such that the problem such as contamination of the head due to dropout of particles does not occur even in use.

Description

Polyester film {Polyester film}

More particularly, the present invention relates to a polyester film excellent in lubricity and abrasion resistance, excellent in slitting property when processed into a magnetic tape, and not subject to dropping even after repeated use.

Polyester represented by polyethylene terephthalate is not only physically and chemically stable but also has high mechanical strength, mechanical properties, heat resistance, weather resistance, durability, chemical resistance and electric insulation, and the film produced by biaxially stretching thereof is used for medical, industrial, They are widely used for capacitors, packaging, photographic films, insulating materials, labels, as well as for magnetic recording media.

The polyester film is usually obtained by feeding a polyester resin together with various additives to an extruder, melt extruding the mixture into a plate, cooling and solidifying the mixture to form a sheet, and uniaxially or biaxially stretching the sheet.

In order to use the polyester film thus obtained in a versatile manner, the winding workability, the processability of the post-processing, the running property, the surface property, the lubricity and the like should be excellent. Accordingly, various methods for imparting good lability to the film have been attempted.

Among these methods, inert inorganic particles such as calcium carbonate, silica, alumina, and kaolin are added during the production of polyester to form irregularities on the surface of the film. Other methods include a method in which a phosphoric acid or ester is added to a metal compound used as a catalyst in a polyester polymerization reaction, for example, an alkaline earth metal compound to precipitate fine particles on the surface of the film to thereby make the surface irregular Japanese Unexamined Patent Publication (Kokai) No. Sho-34-5144) or a method in which inert microparticles are added in an extrusion process during the film production process to form protrusions on the surface of the film.

However, when it is attempted to improve the reactivity of the film by the addition of the particulate matter as in the above-mentioned method, the particulate matter acts as an impurity different from the polyester in the stretching process of the film, As shown in Fig. Since these voids scatter light, the formation of a lot of voids significantly deteriorates the transparency of the film. In addition, when the film is running, the void portion is easily broken and the abrasion resistance is poor. In addition, when the film is used for an insulating material or a capacitor, a side effect such as breakdown of insulation occurs in the void portion.

Accordingly, recently, a method has been proposed for improving the abrasion resistance and imparting lubricity while reducing void formation by adding organic particles having excellent affinity with polyester. For example, JP-A-90-11640 discloses a process for producing voids by adding organic particles such as silicone polyimide, crosslinked styrene-divinylbenzene copolymer, crosslinked polyester, polytetrafluoroethylene and the like and an inorganic lubricant such as calcium carbonate. There is disclosed a method for producing a polyester film in which the occurrence is reduced and the lubricity and the abrasion resistance are improved.

However, in the case of the above patent, there is a problem that sufficient abrasion resistance can not be provided due to lack of strength of the organic particles themselves.

On the other hand, when the polyester film is processed into a magnetic tape, a magnetic material is applied to the film, and then the tape is processed by slitting the film to an appropriate width. At this time, as described above, in order to improve the lubricity of the film, the added particles are not smooth due to the stress applied to the slitting knife, resulting in debris, or the height of one or both ends of the tape wound on the roll A high edge phenomenon occurs which is relatively higher than the center portion.

The debris generated as described above has a problem of increasing the dropout. The high edge not only deteriorates the appearance of the rolled tape, but also causes a loss of function as a tape due to poor recording and reproduction of the edge portion .

In order to improve such a phenomenon, a method of changing a stretching method, a method of controlling a refractive index or a degree of crystallization of a film, and the like have been considered, but the effect is insignificant.

In addition, magnetic tapes with a higher copying speed are required according to recent trends of image and music publications. When high-speed copying is performed, friction between a video head and a magnetic tape is increased. Therefore, It becomes easy to drop out, and the dropped particles cause a problem such as contamination of the head of the copying machine.

Disclosure of Invention Technical Problem [8] The present invention provides a polyester film which is excellent in lubricity and abrasion resistance, has an excellent slitting property when processed into a magnetic tape, and does not cause particle dropout even during high-speed copying.

The technical problem of the present invention is that 0.01 to 2.0 parts by weight of needle-shaped particles insoluble in polyester and 0.01 to 3.0 parts by weight of insoluble platelike particles are contained in the polyester, based on the total weight of the polyester, . ≪ / RTI >

In the polyester film according to the present invention, it is preferable that the main repeating unit of the polyester is at least one selected from the group consisting of ethylene terephthalate and ethylene naphthalate.

The acicular particles may be any of those satisfying the object of the present invention. Preferably, acicular particles having an acicular ratio of 4 to 50 and an average particle diameter of 0.01 to 2.0 탆 are used. The acicular particles include kaolin, mordenite, asbestos, wollastonite, carbon Fibers, silicon nitride, silicon carbide, hard calcium carbonate, iron oxide and iron oxide, and ferric oxide.

If the acicular shape ratio of the acicular particles is less than 4, the desired slitting effect of the present invention can not be obtained. On the other hand, if the acicular shape ratio is more than 50, entanglement of particles tends to occur.

On the other hand, the average particle size of the acicular particles is preferably 0.01 to 2.0 탆, more preferably 0.1 to 1.5 탆 as described above. If the average particle diameter is less than 0.01 탆, the size of the irregularities formed on the surface of the film is so small that the reactivity is poor, and when the average particle diameter exceeds 2.0 탆, the surface of the film is roughened and the electronic characteristics are poor.

If the content of the needle-shaped particles is less than 0.01 part by weight, the number of irregularities formed on the surface of the film is low and the activity is poor. On the other hand, if the content is more than 2.0 parts by weight, the film is roughened.

The plate-like particles may be any of those suitable for the purpose of the present invention, but may be any of plate-like kaolin, mica, plate-like silica, plate-like calcium phosphate, boron nitride, talc, Synthetic mica and the like can be used.

On the other hand, the average particle diameter of the above-mentioned plate-like particles is preferably 0.01 to 5.0 탆, more preferably 0.1 to 3.0 탆 as described above. When the average particle diameter is less than 0.01 탆, the size of the irregularities formed on the surface of the film is small and the reactivity is poor. On the other hand, when the average particle diameter exceeds 5.0 탆, the surface of the polyester film becomes roughened and the electronic characteristics become poor.

When the content of the plate-like particles is less than 0.01 parts by weight, the number of unevenness formed on the surface of the film is low, and the lubricity is poor. When the content is more than 3.0 parts by weight, the film is roughened.

In order to enhance the effect of the present invention, inorganic or organic particles insoluble in polyester may be used in addition to the above-mentioned needle-shaped and plate-like particles. In consideration of the object of the present invention, particles capable of forming appropriate irregularities are selected and used Or two or more of these particles may be used in combination.

In order to improve the affinity between the particles and the polyester, the surface of the polyester film may be treated with a known surface treatment agent.

The polyester film according to the present invention can be produced according to a usual production method, and the acicular particles and the plate-like particles and the inorganic or organic particles insoluble in the polyester can be added at any time before the completion of the polymerization reaction .

Hereinafter, a general method for producing a polyester film according to the present invention will be described.

First, the polyester molten resin is prepared by adding the acicular particles and the plate-like particles, and optionally one or more inorganic or organic particles insoluble in the polyester, at any point in the production of the polyester molten resin, To produce a molten sheet. After the electrostatic charge is applied to the above-mentioned molten sheet by the electrostatic applying means, the molten sheet to which the static electricity is applied is adhered to the cooling means and solidified to produce an unoriented sheet, and then uniaxially stretched or biaxially stretched in the longitudinal and transverse directions, An ester film can be produced. In this case, the longitudinal stretching can be carried out in a single step or in a multistage manner. In order to improve the adhesiveness and antistatic property of the film, an in-line coating process is performed between longitudinal stretching and transverse stretching, The corona treatment may be performed.

The polyester film of the present invention thus obtained is excellent in both slipping property and repeated usability as well as lubricity and abrasion resistance as well as magnetic tape.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited thereto.

In the present invention, evaluation of the physical properties of the film was carried out in the following manner:

1) needle bed ratio

The length-to-thickness ratio of 500 particles was measured using a scanning microscope (× 50), and the average value of these was calculated.

2) Average particle size and particle shape

Fifty portions of particles enlarged by 50,000 magnifications with a scanning microscope were arbitrarily taken and photographed, and then the values obtained from the respective sites were measured by an image analyzer and the average value thereof was taken as an average particle size. , Acupuncture, spherical or massive.

3) Active

Using a TRT-300D (manufactured by Yokohama Institute of Technology, Japan), the tape was slit with a width of ½ inch, and the travel speed was 300 m / min., The pulling tension was 100 g and the contact angle with the pin was 135 °. The running friction coefficient was measured from the winding tension after passing the pin (material SUS303) through 1500 m using the following equation (1).

占 K = [2.303 /?] 占 log [Ti / To]

(Where? Is the contact angle between the film and the guide pin, and Ti and To are the take-in and take-up tension, respectively)

4) Abrasion resistance

After the completion of the above-mentioned activity measurement, the degree of the whiteness on the surface of the fixed guide pin was divided into four grades and evaluated.

◎: When almost no white powder is attached to the guide pin

○: When the area of 5% or less of the area of the guide pin is covered with white powder

△: When the area of 10% or less of the area of the guide pin is covered with white powder

X: When the area exceeding 10% of the guide pin area is filled with 100 parts

5) Slitting property

The cross section 50 of the slit film was magnified 50,000 times by using a columnar electron microscope and classified into the following four grades depending on the number of damaged portions having a size of 50 μm or more.

◎: When the number of damaged parts is 0 to 5

○: When the number of damage sites is 6 to 10

?: The number of damage sites is 11 to 19

X: When the number of damaged parts is 20 or more

6) Overall evaluation

The results of comprehensive evaluation of various physical properties of the polyester film measured in the above-described manner are shown in the following four grades.

◎: Very good

○: Good

△: Normal

X: Bad

[Example 1]

100 g of dimethyl terephthalate, 70 g of ethylene glycol, and 0.05 g of calcium acetate were fed into the reactor, and the transesterification reaction was carried out for 4 hours. After completion of the reaction, 0.3 g of acicular kaolin particles having an acicular ratio of 8 and an average particle diameter of 0.4 탆 and 0.1 g of platemagic acid particles having an average particle diameter of 0.5 탆 were added to the reactor, and then 0.06 g of trimethyl phosphate and 0.04 g of antimony trioxide were added And subjected to a polycondensation reaction for 5 hours by a conventional method to prepare a polyester.

The polyester was dried, put into an extruder maintained at 290 ° C, melt-extruded, and closely contacted with a rotating cooling drum to produce an unstretched sheet. Next, the non-stretched sheet was stretched 3.5 times at 90 DEG C in the longitudinal direction and 4.3 times at 110 DEG C in the transverse direction, and then heat-treated at 210 DEG C for 3 seconds to produce a polyester film having a thickness of 15 mu m.

Next, various properties of the polyester film were measured according to the above-mentioned method, and the results are shown in Table 1 below.

[Example 2]

Except that acicular kaolin particles and plate-like mica particles were replaced by 0.2 g of wollastonite particles having an acicular ratio of 20 and an average particle diameter of 0.6 탆, and 0.3 g of platelike kaolin particles having an average particle diameter of 0.8 탆, After preparing a polyester film, various physical properties of the film were measured, and the results are shown in Table 1 below.

[Example 3]

Except that the acicular kaolin particles and the plate-like mica particles were replaced by 0.2 g of iron oxide particles having an acicular ratio of 25 and an average particle diameter of 0.6 탆 and 0.3 g of plate-like kaolin particles having an average particle diameter of 0.5 탆, , And various physical properties of the film were measured. The results are shown in Table 1. < tb > < TABLE >

[Comparative Example 1]

A polyester film was produced in the same manner as in Example 1 except that 0.3 g of bulk calcium carbonate having an average particle diameter of 0.5 탆 was added instead of acicular kaolin particles and plate-like mica particles, and then various physical properties of the film were measured The results are shown in Table 1 below.

[Comparative Example 2]

A polyester film was produced in the same manner as in Example 1, except that acicular kaolin particles and plate-like mica particles were replaced with 0.3 g of acicular kaolin particles having an acicular ratio of 3 and an average particle diameter of 0.5 탆, The results are shown in Table 1 below.

[Comparative Example 3]

A polyester film was prepared in the same manner as in Example 1, except that 0.3 g of mica particles having an average particle diameter of 0.5 탆 was added instead of acicular kaolin particles and plate-like mica particles, and various physical properties of the film were measured The results are shown in Table 1 below.

[Comparative Example 4]

Except that acicular kaolin particles and 0.3 g of acicular kaolin particles having an average particle size of 0.5 탆 and an average particle size of 0.8 탆 and 0.1 g of an acicular phase ratio of 3 were used instead of acicular kaolin particles and plate- , And various physical properties of the film were measured. The results are shown in Table 1 below.

Particle name shape Needle bed ratio Average particle diameter (占 퐉) Content (g) Active Slitting Abrasion resistance Overall assessment Example 1 Kaolin mica Acupuncture 81.6 0.40.5 0.30.1 0.28 ◎ ◎ ◎ Example 2 Wollastonite kaolin Acupuncture 201.5 0.60.8 0.20.3 0.29 ◎ ◎ ◎ Example 3 Oxidizing agent 2 iron kaolin Acupuncture 251.1 0.60.5 0.20.3 0.32 ◎ ◎ ◎ Comparative Example 1 Calcium carbonate Mass 1.5 0.5 0.3 0.31 × △ × Comparative Example 2 kaoline couch 3 0.5 0.3 0.33 △ △ × Comparative Example 3 Mica Plate 1.6 0.5 0.3 0.31 × ○ × Comparative Example 4 Kaolin mica Acupuncture 31.6 0.50.8 0.30.1 0.30 △ ◎ △

From the results shown in Table 1, the polyester films (Examples 1 to 3) containing the needle-shaped and plate-like particles in which the needle ratio, the average particle diameter and the content correspond to the category of the present invention, Is excellent. On the other hand, in the case where the needle-like ratio deviates from the scope of the present invention (Comparative Example 4), the physical properties of the polyester film were not so good, only the needle-like or plate-like particles were contained (Comparative Examples 2 and 3) (Comparative Example 1), it was found that the physical properties of the polyester film were generally poor.

The polyester film according to the present invention not only improves lubricity and abrasion resistance by containing a predetermined amount of needle-shaped or plate-shaped particles whose needle bed ratio and average particle size are controlled, but also has good slitting property at the time of processing into a magnetic tape, There is an advantage such that the problem such as contamination of the head due to dropout of particles does not occur even in use.

Claims (3)

Wherein the main repeating unit is at least one polyester selected from the group consisting of ethylene terephthalate and ethylene naphthalate and is insoluble in said polyester based on the total weight of said polyester and has an acicular ratio of 4 to 50 and an average particle diameter of 0.01 to & 0.01 to 2.0 parts by weight of needle-like particles having a mean particle size of 2.0 to 2.0 占 퐉 and 0.01 to 3.0 parts by weight of a plate-like particle insoluble in the polyester and having an average particle size of 0.01 to 5.0 占 퐉. The method of claim 1, wherein the acicular particles are selected from the group consisting of kaolin, mordenite, asbestos, diluted silica, carbon fiber, silicon nitride, silicon carbide, light calcium carbonate, Lt; / RTI > film. The polyester film according to claim 1, wherein the plate-like particles are selected from the group consisting of kaolin, mica, plate-like silica having a plate-like shape, plate-shaped calcium phosphate, boron nitride, talc and synthetic mica.