JPS595216B2 - polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyester film containing a crosslinked polymer covalently bonded to a polyester.

Today, biaxially stretched polyester films, especially polyethylene terephthalate, have excellent properties such as tensile strength, tear strength, modulus of elasticity, transparency, chemical resistance, and heat resistance, and are used for gold and silver thread, transfer marks, and plate making. , for female molds, for photographs, etc., as well as electrical insulating materials, capacitor dielectrics,
It is widely used in many fields such as magnetic recording media. However, such polyester films have different required properties depending on their use. For example, so-called translucent films used for gold and silver thread, transfer marks, plate making, mold release, etc. have poor workability when handling the film. Particularly desirable is one that is excellent and does not impair transparency.

In addition, when magnetic tape is used as an audio, video or computer magnetic recording medium, it is required to have a low coefficient of friction, good wear resistance, and no loss of electromagnetic conversion characteristics.

Furthermore, for capacitor dielectrics, polyester films with excellent workability, resistance to protrusion deformation, electrical properties, etc. are desired. A common characteristic required for all uses of polyester films including these is excellent workability when handling the film, and to improve this, it is necessary to reduce the slipperiness of polyester films, that is, the coefficient of friction. There is.

For this purpose, a method using an antistatic agent or a lubricant has been proposed, but it is difficult to put it into practical use because of the deterioration of electrical properties, the decrease in work efficiency, and the increase in cost. Various methods have been proposed to improve slipperiness, but the most
- A commonly used method is to include inert particles in the film, and this method can be broadly divided into two. One method is called the precipitation method, in which when a calcium compound is used as a transesterification catalyst, fine particles of the calcium salt of the polyester oligomer that is formed and precipitated in the polyester are used. A method of further adding terephthalic acid to the system of
All methods, such as adding terephthalic acid and calcium acetate during the polymerization step to produce a calcium salt of polyester oligomer, precipitate fine particles in the reaction system.

There is also a method in which fine particles are precipitated by a similar method using a lithium compound instead of a calcium compound. When attempting to improve slipperiness using these fine particles, the amount and particle diameter of precipitated particles tend to change, making it difficult to control slipperiness. Another disadvantage is that the film has insufficient slipperiness in spite of its high turbidity, and when recycled, it no longer retains its original slipperiness. Another method that is compared to the precipitation method is the addition method, in which kaolin, talc, silica, calcium carbonate, calcium phosphate, lithium phosphate, etc. are added as they are or after being made into fine particles during polyester synthesis or molding. be.

The method of adding these inorganic compounds can adjust the particle size and amount of fine particles, and these fine particles are not easily destroyed even by stretching, so the reproducibility of results is good, but unnecessary coarse particles are often mixed in. do. In order to remove these coarse particles, a classification operation and, if necessary, a pulverization operation as a pretreatment are necessary, which makes the operation complicated and increases the cost. Moreover, even after such operations, the contamination of coarse particles cannot be avoided. Furthermore, even if fine particles with very few coarse particles are obtained, it is generally extremely difficult to uniformly disperse an inorganic compound in polyester, which is an organic substance. The presence of foreign substances other than particles, coarse particles of inorganic compounds, or agglomerated particles due to poor dispersion will have a negative effect on the electrical properties of films for capacitors, and may deteriorate the electromagnetic conversion characteristics of films for magnetic tapes or cause white powder. This causes problems such as dropouts and deterioration of film quality.

Attempts have also been made to use a combination of appropriate amounts of precipitated particles and additive particles, but this has not solved the essential drawbacks of each, and on the contrary, the film manufacturing process itself has become complicated, and biaxially stretched films have Industrial problems such as the need to change the blending ratio appropriately when the end portion is used as a recycled product are coming into focus.

The present inventors conducted extensive studies in view of the above circumstances and obtained the following findings.

That is, the biggest drawback of the precipitated or added particles that have been used to improve the slipperiness of polyester films is their lack of affinity with polyester.

Therefore, particles are peeled off from the polyester film due to abrasion between the polyester films or between the polyester film and other substrates, causing white powder and dropouts in, for example, magnetic tape films. Furthermore, since large voids are formed around the particles during stretching, transparency is impaired. This lack of affinity also causes aggregation of particles, impairing transparency and aesthetics, and if the aggregation is particularly severe, the filter during film formation can become severely clogged, and in some cases, the film may break. It becomes like this. The presence of agglomerated particles is especially fatal for capacitor films and significantly reduces electrical properties. The present inventors particularly investigated the improvement of the affinity between these particles and polyester, and as a result, they found a crosslinked polymer fine powder (hereinafter simply referred to as polymer fine powder) having a group capable of covalently bonding with polyester.

). That is, the present invention provides a compound having only one aliphatic unsaturated bond in the molecule,
A crosslinked polymer with a degree of crosslinking of 8 to 50% and an average particle size of 0.1 to 5μ obtained by copolymerization with a compound having two or more aliphatic unsaturated bonds in the molecule is 0.001 to 4 % by weight, and the polymer is substantially covalently bonded to the polyester.

The present invention will be explained in more detail below.

The polyester film of the present invention is made from a polymer mainly composed of polyethylene terephthalate, for example, a copolymer with polyethylene terephthalate or another third component, and in the case of a copolymer, 80 mol% or more is ethylene. Terephthalate units are preferred.

A polyester film is obtained by melt-stretching these raw materials as they are or blending them with other polymers or various additives to form a melt film. Polyester can be produced by using terephthalic acid or its ester-forming derivatives such as dimethyl terephthalate and ethylene glycol as main starting materials and polymerizing them in a conventional manner.

The polymer production process usually takes a two-step process in which a polyester oligomer is obtained by performing a transesterification reaction or an esterification reaction, and then a polycondensation reaction is carried out. One or more of compounds, zinc compounds, lithium compounds, etc. can be used.

Further, after the transesterification reaction or esterification reaction is substantially completed, 51 or more types of phosphorus compounds may be added as a regulator or heat stabilizer for precipitated particles. As the polycondensation catalyst, one or more of known antimony compounds, germanium compounds, titanium compounds, tin compounds, cobalt compounds, etc. can be used, but antimony compounds and germanium compounds are particularly preferred.

Since the fine polymer powder used in the present invention is itself an organic substance, it is far more compatible with polyester than inorganic compounds.

However, the dispersibility of fine polymer powders such as polytetrafluoroethylene, which do not have groups that react with polyester, is not always sufficient and coarse particles are often formed. Therefore, in order to disperse the fine polymer powder sufficiently uniformly, in the present invention, particles having a functional group that can react with a carboxyl group or a hydroxyl group are used, and this functional group and a carboxyl group, a hydroxyl group, or an ester of the polyester are used. By reaction with the group, the particles are firmly covalently bonded to the polyester and embedded in the polyester.

Examples of groups that can react with such polyesters to form covalent bonds include ester groups, carboxyl groups, hydroxyl groups, epoxy groups, and amino groups. The ester group includes, for example, an acetoxy group, an acyloxy group such as a propionyloxy' group, an alkoxycarbonyl group such as a methoxycarbonyl group, or an ester group such as a phosphate ester group.

Another feature of the fine polymer powder used in the present invention is that it has a crosslinked structure.

That is, the fine polymer powder having the crosslinked structure is insoluble and infusible even at high temperatures during synthesis or molding of polyester, and therefore can be dispersed in polyester while maintaining its original shape at the time of addition. That is, the polymer fine powder may come into contact with methanol,
It is almost insoluble even at high temperatures in alcohols such as ethanol, glycols such as ethylene glycol, propylene glycol, and 1,4-butanediol, bis(β-hydroxyethyl) terephthalate and its oligomers, and even polyester carbonates. It needs to be something.

Specifically, the weight loss of the crosslinked polymer when immersed in each medium at high temperature 1 for 1 hour is 20% compared to the original weight of the crosslinked polymer.
% or less, preferably 10% or less. Further, the fine polymer powder must not melt even at high temperatures during polyester production or molding, that is, at temperatures of about 260 to 295°C.

The fine polymer powder used in the present invention will be explained in more detail below.

The fine polymer powder of the present invention includes a compound A having only one aliphatic unsaturated bond in the molecule, and a compound (B) having two or more aliphatic unsaturated bonds in the molecule as a crosslinking agent.
) is used.

Examples of compounds that are one component of the copolymer include acrylic acid, methacrylic acid, lower alkyl esters thereof such as methyl ester and ethyl ester, or glycidyl ester, maleic anhydride and its alkyl derivatives,
Examples include vinyl glycidyl ether, vinyl acetate, and styrene derivatives having the above-mentioned active groups that can be covalently bonded to polyester. Examples of the compound (F3) include divinylbenzene and divinylsulfone. One or more types of each of the compounds Vj3, ) and old) are used, but ethylene or styrene may be further added to these systems for copolymerization. Further, a compound having a nitrogen atom may be copolymerized. Fine polymer powders containing nitrogen atoms tend to give polyester a color, especially a yellowish tinge.
It can be used in applications where coloring is not a problem. Typical examples of these copolymers include copolymers of methyl methacrylate and divinylbenzene, or methyl acrylate and divinylbenzene.

In addition, by saponifying these fine polymer powders having alkyl ester groups or copolymerizing them using methacrylic acid instead of methacrylic esters and acrylic acid instead of acrylic esters, cross-linked polymers containing carboxyl groups can be easily obtained. A molecular fine powder can be obtained. Commercially available weakly acidic cation exchange resins have a crosslinked structure and carboxyl groups, and therefore can be suitably used as the crosslinked polymer used in the present invention. Further, a crosslinked polymer having an alkyl ester group may be used as an intermediate raw material. The polymerization initiator for copolymerizing the compound (2) with the compound may be a well-known chemical radical initiator, such as azoisobutyronitonyl, benzoyl peroxide, t-butyl peroxide, cumene hydroperoxide, etc. Although it is convenient to use ultraviolet irradiation, polymerization may also be initiated simply by heating.

As described above, the crosslinked polymer used in the present invention must be capable of forming a covalent bond with the hydroxyl group or carboxyl group in the polyester, and the concentration of the functional group is 1 to 15 equivalents per 1K9 of the crosslinked polymer. , especially 3-15
Equivalent amounts are preferred.

The average particle size of the crosslinked polymer used in the present invention is 0.1
It should be ~5μ. If the average particle size is less than 0.1 μm, the surface roughness of the film containing the particles will be small, the slipperiness imparting effect will be insufficient, and the abrasion resistance will also be unsatisfactory. On the other hand, if the average particle size exceeds 5 μm, the electromagnetic conversion characteristics and electrical characteristics will deteriorate, and the life of the filter during film formation will be shortened and the frequency of filter replacement will increase, resulting in a decrease in productivity. In order to obtain the particles used in the present invention with an average particle size of 0.1 to 5μ, there is a method of directly obtaining the monomer as a raw material by suspension polymerization or emulsion polymerization, but there are It is difficult to obtain uniform and fine particles with good reproducibility using this method because the particle size easily changes due to slight variations in the concentration, impurities, etc.

Therefore, by crushing and classifying crosslinked polymers with a size of several tens of microns to several hundred microns, which can be easily obtained especially in the case of suspension polymerization, fine powder with an average particle size of 0.1 to 5 microns can be obtained. The method of obtaining it is practical. Suitable methods for grinding particles include, for example, jet mills, fluid energy mills, and ball mills. Among these, jet mills and fluid energy mills are particularly preferably used. Of course, two or more of these pulverization methods may be used in combination to pulverize in stages. The particles thus pulverized are sent to the next classification step as necessary in order to obtain particles of a constant particle size suitable for use in the present invention.

Classification methods include, for example, a semi-free whirlpool method, a forced whirlpool method, a hydrocyclone method, and a centrifugation method, and any of these methods may be employed. Of course, the classification step may be omitted if fine particles with a practical particle size distribution can be obtained only by the pulverization step. By the method described above, it is possible to obtain a crosslinked polymer fine powder having an average particle size of 0.1 to 5 μm, which is necessary for the present invention.

In general, the particle size of the added fine polymer powder is maintained in polyester, but in the case of fine polymer powder with a low degree of crosslinking, it often swells in polyester and the particle size becomes somewhat larger.

In this case, in order to give the desired average particle size in the polyester, it is sufficient to add particles with an average particle size after subtracting the particle size corresponding to swelling in advance. The degree of crosslinking of the polymer fine powder obtained from monovinyl compounds and divinyl compounds is 8 to 50.
%, preferably 9 to 45%.

The degree of crosslinking is a numerical value defined by the following formula, but if this value is less than 8%, pulverization becomes difficult, and even if it exceeds 50%, there is no difference in the ease of pulverization, and the density of functional groups decreases, so the bonding strength with polyester becomes poor. Weight of divinyl compound Crosslinking degree = × 100 (%) Total weight of monomer Changing the degree of crosslinking will naturally change the refractive index of the crosslinked polymer, so conversely, this phenomenon can be used to adjust the degree of crosslinking according to the purpose of the polyester film. You can also subtly control the transparency of the film.

For example, in the case of methacrylic acid-divinylbenzene copolymer, which is one of the materials suitable for use as a crosslinked polymer in the present invention, the higher the degree of crosslinking, the closer the refractive index of the resulting crosslinked polymer and biaxially stretched polyester film. Increased transparency. Therefore, in fields where transparency is particularly desired, this requirement can be met by using fine powder with a high degree of crosslinking. In the present invention, such crosslinked polymer fine powder is contained in the polyester film from 0.001 to
It needs to be contained in an amount of 4% by weight, preferably 0.02 to 0.5% by weight, and more preferably 0.03 to 0.2% by weight.

If this amount is less than 0.001% by weight, the effect of imparting slipperiness will be insufficient and there will be no effect of improving wear resistance. On the other hand, if it is used in an amount exceeding 4% by weight, the effect of imparting slipperiness and improving the abrasion resistance will not be further exhibited, and on the contrary, problems such as shortening of the life of the filter during film formation will occur. In the present invention, the fine polymer powder is preferably added at any time during the polyester manufacturing process.

If a film is formed by adding and mixing the polyester in the form of chips or powder after polymerization and extruding it, the reaction time between the fine powder and the polyester is short, and each particle of the fine polymer T powder reacts sufficiently with the polyester. As a result, the affinity is not improved and when a stretched film is formed, voids are generated around the particles and the film peels off from the film surface due to simple abrasion. In the present invention, in order to substantially complete the covalent bond between the polymer fine powder and the polyester, 20
Preferably, the two are allowed to react for at least 4 hours at a temperature above 0°C. Therefore, in the present invention, the timing of addition of the fine polymer powder is preferably before the middle of the polycondensation stage, especially when S.
Preferably, the reaction is carried out before the teller exchange reaction or before the start of the polycondensation reaction.

However, among fine polymer powders, those having carboxyl groups may deactivate the transesterification catalyst if added before the transesterification reaction, so it is preferable to add them after the transesterification reaction has substantially completed. On the other hand, for example, when a polymer fine powder having an ester group is mixed, there is no effect of such a catalyst poison, and it is possible to contact the polyester oligomer for a longer period of time, so it is not necessary to add it before the transesterification reaction. Rather, it is adopted as a preferable condition. Of course, the purpose can be fully achieved by adding these various particles after the transesterification reaction is substantially completed and before the polycondensation reaction is started. In any case, it is necessary that the particles used be covalently bonded to the polyester, but in the present invention, it can be confirmed that the two have actually reacted, for example, by the following method.

In other words, the rate of formation of a covalent bond between the polyester and the functional group of the crosslinked polymer depends on the type and concentration of the end group of the polyester, the type and concentration of the functional group of the crosslinked polymer, and the type and reaction polarity of the reaction medium. Although different, for example, bis-(β-hydroxylethyl) terephthalate (hereinafter referred to as BHET), which is a monomer of polyethylene terephthalate, and a methacrylic acid-divinylbenzene copolymer with an average particle size of 2.5μ (divinylbenzene content 10% by weight, or less) MA-DVB
Abbreviated as copolymer.

) at 200°C and measured the decrease in carboxyl groups and increase in ester groups in the -MA-DVB copolymer using the method described below, the esterification rate was approximately 60% in 3 hours and 6 hours. It was almost 100%. Measuring method of esterification rate: The reaction product 1001 of crosslinked polymer and polyester (or BHET) was mixed with phenol/
Tetrafluoroethane mixed solvent (1/1 weight ratio) 9009
After heating and dissolving Nitori, filter paper (Toyo Roshi Co., Ltd. A6)
The filtered product was washed with 50% phenol/tetrachloroethane mixed solvent and then with 50% chloroform, and then dried under reduced pressure at 90°C for 5 hours.

Next, accurately weigh about 0.11 g of the dried filtrate, put it in a test tube, add 10 g of 0.2N sodium hydroxide, and let it stand at room temperature.
After stirring for an hour, let it stand for a day and night, remove 5 g of the supernatant and 0.1 g.
Back titrate with normal hydrochloric acid.

The carboxyl group concentration in the crosslinked polymer is calculated using the following formula.

0.2 x fl x 10 - 0.1 x F2 Weighed weight of the filtrate [I] y: Amount of hydrochloric acid required for back titration [1] The esterification rate can be determined by the following formula using the measured carboxyl group concentration.

A-B Esterification rate x 100C%] A Here, A: Carboxyl group concentration before reaction [equivalent/l] B: Carboxyl group concentration after reaction [equivalent/K9] Carboxyl in this MA-DVB copolymer The reaction of the group with the polyester-forming component to form a covalent bond can also be confirmed by the following method.

That is, in the infrared absorption spectrum of the MA-DVB copolymer before reaction, the absorption of 170 (P!L-l) based on the carboxyl group is clearly recognized, but the 1730
Absorption of ~1740CWL-l is not observed at all.

However, when the infrared absorption spectrum was examined after reacting the particles with BHET at 200°C for 6 hours, the result was 1730 ~
Although strong absorption is seen in 1740-1, 1700C
No absorption of TfL-1 could be observed. This result agrees with the result obtained from the measurement of the esterification rate.
Note that in the crosslinked polymer having a group capable of covalently bonding with the polyester used in the present invention, all of its functional groups do not necessarily need to react with the polyester.

In other words, the effect of the present invention can be achieved if most of the functional groups located on the surface layer of the crosslinked polymer react, but the amount of these functional groups varies depending on the type, concentration, particle size, etc. of the functional groups. In some cases, it may be on the order of several mol% of the total functional groups.

As for the method of adding the polymer fine powder to the polymer production process, it is preferable to add it as an ethylene glycol slurry.

The appropriate slurry concentration is about 0.5 to 20% by weight. It goes without saying that the fine polymer powder and ethylene glycol may be reacted in advance and then added. The polyester necessary to obtain the polyester film of the present invention can be obtained for the first time by the method detailed above, and the desired film can be produced by forming the polyester as it is or by diluting it with other polyester. .

Other polyesters used for dilution include polyesters produced by conventional precipitation methods or addition methods, or polyesters that do not contain particles, but in either case, the polymer is present in the final polyester film. It is necessary to contain 0.001 to 4% by weight of fine powder. In order to obtain such a film, a known film-forming method is used, for example, it is usually melt-extruded into a film at 270 to 295°C, made into an amorphous sheet, and then sequentially or simultaneously biaxially stretched vertically and horizontally. , heat treatment at 160 to 240°C (for example, the method described in Japanese Patent Publication No. 30-5639) can be employed.

As mentioned above, a polyester film containing a specific amount of a crosslinked polymer with a specific particle size that is substantially covalently bonded to polyester is difficult to agglomerate because the polymer fine powder is uniformly dispersed in the polyester. Since the fine polymer powder is strongly bonded to the polyester, there is a good affinity between the polyester and the fine polymer powder, preventing the formation of voids during stretching and the formation of coarse particles from the film surface. No peeling of particles.

The degree of affinity can be expressed by a numerical value measured by the following method.

That is, an unoriented film with a thickness of 300μ was stretched 3.5 times in both the longitudinal and transverse directions at a speed of 7000%/min at 85°C, and the average length of the long and short axes of the particles in the film and the The ratio of the average length of the long axis to the short axis of the voids generated around the particles is determined, and the arithmetic average of this value for each particle is 0.7 or more, and more preferably 0.8 or more for the film of the present invention. is obtained.

The film of the present invention has better slip properties, and even if the edges of the biaxially stretched film are recycled, the properties of the film obtained will not deteriorate, so it can be used in a wide variety of applications.

Applications in which the characteristics of the film of the present invention are particularly exhibited will be explained in more detail below. Nowadays, polyester films mainly composed of polyethylene terephthalate are widely used as base films for magnetic tapes, but in this case the following required characteristics must be satisfied.

That is, the reduction of white powder in the magnetic tape manufacturing process, the slipperiness of the film, and the excellent frequency characteristics of the input and output of the produced magnetic tape, called electromagnetic conversion characteristics.

Generally, polyester magnetic tape is manufactured by the following process.

That is, the polyester base film is introduced into a coating tank via guide rolls and a magnetic layer is applied thereto. Next, it is magnetized and then subjected to a drying process, passed through a calendar roll, and then slit to form a magnetic tape. The most problematic issue in this series of steps is the generation of so-called white powder.

The present inventors investigated the generation of this white powder in detail and found that it is generated mainly from two places. That is, it has become clear that in addition to the white powder on the calender roll after the magnetic layer is applied (hereinafter referred to as white powder A), there is also white powder on the guide roll and coater (hereinafter referred to as white powder B) in the magnetic layer coating process. On the other hand, the coefficient of friction of the film is directly related to the running properties of tapes for tape recorders, and must be kept as low as possible.

Further, electromagnetic conversion characteristics are unique characteristics required of magnetic tapes, and are expressed as output characteristics with respect to frequency.

Although it is extremely difficult to simultaneously satisfy the above three properties, that is, generation of white powder, coefficient of friction, and electromagnetic conversion properties, the present inventors have developed the polyester of the present invention, which has a specific particle size that is substantially covalently bonded. The above three properties can be achieved by using a polyester film containing a specific amount of an insoluble and infusible crosslinked polymer, and more preferably by controlling the degree of crystallinity of the film to be within a specific range.

1. In order to use the film for magnetic tape, the amount of crosslinked polymer contained in the film is preferably 0.01 to 1% by weight, more preferably 0.02 to 0.5% by weight.

If the content of the crosslinked polymer is too low, the film will have insufficient slipperiness as a magnetic tape film, and it will be difficult to prevent white powder A from forming. On the other hand, if it exceeds 1% by weight, the generation of white powder B increases and the electromagnetic conversion characteristics tend to deteriorate. Although the generation of white powder A and B can be suppressed to a practically acceptable level by the above-mentioned method, some white powder A is still generated.

In order to completely suppress the generation of white powder A, the crystallinity of the film containing the fine polymer powder must be 33 to 46%, preferably 36 to 44%. Crystallinity is 4
When it exceeds 6%, a slight amount of white powder A is observed even in the film containing the fine polymer powder. Also, the crystallinity is 3
Even if it is less than 3%, the effect of preventing the generation of white powder A will no longer change, and on the contrary, the shrinkage rate of the film will become larger than necessary.
The degree of crystallinity can be adjusted by changing the conditions during film formation, but specifically, the stretching temperature is 80 to 120°C, the stretching ratio is 2.5 to 4.5 times in both length and width, and heat setting is performed. temperature is 1
The heat setting time is selected from the range of 50 to 250°C and 1 to 10 seconds. Among these, the heat setting conditions are particularly related to the crystallinity of the obtained film, and the higher the heat setting temperature and the longer the heat setting time, the higher the crystallinity. This value cannot be determined unconditionally as it depends to some extent on the size, structure, film thickness, etc. of the heat treatment chamber, but for example, the heat setting temperature is 200 to 220°C and the heat setting time is 2 to 7 seconds. The crystallinity of the film obtained can be approximately 44 to 50%.

Keeping other conditions constant, only the heat fixing temperature is 160-180.
If the temperature is lowered to .degree. C., a film with a crystallinity of about 38 to 42% can be obtained. In addition, as a film for magnetic tape, 6
A film thickness of ~30μ is preferred. The film of the present invention is also extremely useful as a polyester film for capacitors.

There are two types of plastic capacitors: vapor-deposited capacitors and foil-wound capacitors, and the characteristics required of the film for both are similar.

That is, the first characteristic required is an improvement in workability when handling the film, that is, a reduction in the coefficient of friction.

Also, as a film for capacitors, it goes without saying that electrical properties are important. The electrical properties to be evaluated mainly include dielectric strength and the product of capacitance and electrical resistance called CR value. Another important property required of capacitor films is resistance to ejection deformation.

This phenomenon of protruding deformation is a phenomenon in which the film bulges up in parts due to dust getting mixed in when the film is wound into a roll.In the protruding deformed area, the film deforms into a ring shape, which reduces the dielectric strength. The product value decreases due to the poor winding appearance of the roll. The thinner the film, the more likely this phenomenon of protrusion deformation will occur. When used as a capacitor film, 0.01 to 1% by weight, preferably 0.02 to 0.5% by weight of the films of the present invention having crosslinked polymers having an average particle size of 0.3 to 5μ. A film containing the above is preferred.

If the average particle size is less than 0.3 μm, the film tends to have insufficient slipperiness as a capacitor film and has poor ejection deformation resistance.

On the other hand, when the average particle size exceeds 5 μm, the dielectric strength becomes poor. Furthermore, if the amount of this crosslinked polymer is less than 0.01% by weight, the slipperiness as a capacitor film will be insufficient, and the resistance to ejection deformation will tend to be poor; on the other hand, if it exceeds 1% by weight, However, the effect of imparting slipperiness and resistance to protrusion deformation are not further improved, and on the contrary, the electrical properties, particularly the dielectric strength, tend to be inferior. The film of the present invention containing the fine polymer powder used as a polyester film for capacitors exhibits its maximum effect when its crystallinity is in the range of 45 to 55%, preferably 48 to 53%. Ru.

That is, if the crystallinity of the film is less than 45%, workability during slitting, which is another required property, tends to deteriorate.

That is, this polyester film is slit and used as strips, but if the workability during slitting is poor, the slit portions may locally bulge, impairing the uniformity of the thickness as a capacitor film. On the other hand, if the crystallinity of the film exceeds 55%, the CR value, especially 1
The CR value at high temperatures of 00° C. or higher begins to decrease.

In addition, as a film for a capacitor, it is preferable to set it as a film thickness of 3-12 micrometers.

In the polyester film of the present invention, since the fine polymer powder is uniformly dispersed in the polyester, no coarse particles are formed, and therefore the film is excellent in electrical properties, particularly dielectric strength.

Moreover, since the polymer fine powder is an organic substance, it does not contain any metal elements, and therefore, superior results in electrical properties, particularly CR values, are obtained compared to conventional precipitation methods and addition methods. This point is particularly important to emphasize, and even if coarse particles of the fine polymer powder were to be mixed in due to trouble in the classification process, the effect would be much smaller than in the case of conventional inorganic compounds. Furthermore, the film of the present invention is extremely useful as a polyester film for vapor deposition.
In other words, for gold and silver threads and transfer marks, metals such as aluminum and zinc are vapor-deposited and slit as necessary. It is excellent in that it is excellent in terms of the difference between the front and back sides during vapor deposition and in terms of thread breakage when winding up the slit strips. In the case of a polyester film for vapor deposition, among the films of the present invention, the average particle size is 0.
, 3-5μ, preferably 0.5-3μ, content 0.02
-0.5% by weight, preferably 0.03-0.2% by weight.

As described in detail above, according to the present invention, unlike the conventionally known blends of polymers and crosslinked polymers, polyester and crosslinked polymers are covalently bonded to each other. It is particularly suitable for magnetic tapes, capacitors, and vapor deposition, and can also be used for packaging, plate making, mold release, transfer marks, photography, etc. EXAMPLES The present invention will be explained in more detail with reference to examples below, but the present invention is not limited to the following examples unless the gist of the invention is exceeded.

The various physical properties were measured using the following methods.

Average particle size: I went to the microscope.

That is, the particles or the polyester containing the particles were sandwiched between cover glasses, and the maximum particle size was measured after taking a photograph. The average particle size refers to the particle size expressed by the diameter at the point of weight fraction 509b by calculating the weight distribution of the particle group with the maximum diameter as the diameter. Sliding property: Represented by the coefficient of friction, and the coefficient of friction was measured in accordance with ASTM D-1894 using an improved method so that it could be measured using a tape-shaped sample.

The size of the sample at the time of measurement was 15 cm wide and 150 cm long.
The recommended tensile speed is 20 Rm/Rm/π. The measurements were carried out in an atmosphere with a temperature of 21±2° C. and a humidity of 65±5%.
White powder: A sample to be evaluated was passed through the magnetic tape manufacturing process, and the weight of white powder (white powder A) generated on a calender roll was measured and expressed as a relative value.

On the other hand, white powder (white powder B) generated in the guide roll and coater
) was also weighed in the same manner and expressed as a relative value.

The smaller the value in each item, the better.

Electromagnetic conversion characteristics: Evaluation was performed by expressing the decrease in output relative to a blank at 10,000 cycles/sec in decibels (Db).

This value is acceptable if it is within -0.5 db. Crystallinity:
The degree of crystallinity is calculated using the density method (published on June 10, 1961,
Polyester Fiber Co., Ltd. Coronasha, written by Hiroshi Yokouchi and Itaru Nakamura 2
(page 00).

Dk (d-Da) That is, crystallinity Xc = ×100 (%) d(Dk-Da) It is expressed as

Here, Da: Density of amorphous 1.3311/1 Dk: Density of crystalline 1.4551/Dd: Density of sample
34), the voltage rise rate is (), IKV/sec, and the thickness is 6.
The dielectric breakdown voltage of μ biaxially oriented polyester-7 film was measured.

The higher this value is, the better the dielectric strength is. CR value: Measurement of capacitance C was carried out under the conditions of 1 KHz and 0.3 Vrms using "RLC DigiBridge" manufactured by General Radio Co., Ltd., and measurement of electrical resistance and R was carried out using a super insulation resistance meter manufactured by Yokogawa Hyuretsu Card Co., Ltd. After applying a DC voltage of 100 V, the power value was read 1 minute later.

The product of both is the CR value (ΩF). The measurement was conducted at 125℃.
I did it at Resistance to protrusion deformation: Count the number of wraps required for the partial bulge in the film that was caused by intentionally adding particles with an average particle size of 10 μm during film winding to disappear, and divide the film into 3 ranks: A, B, and C from best to worst. Ta.

Workability during slitting: The degree of swelling of the slit area when polyester film is slit was observed using an electron microscope.
Divided into ranks.

A: There is almost no mound, and the shape of the roll is good.
C has a large mound (0.3μ or more) and the end portion swells when rolled, and B has a middle portion between the two. Film turbidity: Measured using a Nippon Denshoku turbidimeter model NDH-2A according to the method of ASTM DlOO3-61.

Difference between front and back: Introduce the film to be evaluated to the vacuum deposition equipment 1
0-゛TOrr. Metallic aluminum was deposited under high vacuum.

After vapor deposition, a part of the vapor-deposited film was cut out and divided into equal parts, and then one sheet was turned over and lined up to visually determine the difference between the front and back sides. 2
The results were divided into two ranks and the superior one was designated as A.

Thread breakage: Microslit the aluminum vapor deposited film to 0.
The relative value of the number of yarn breakages when a film with a width of 5 mm is wound to a certain length is shown.

The smaller this value is, the fewer the number of thread breakages occurring under the same conditions. Intrinsic viscosity: 30.0 by dissolving polyester chips 1.08 in phenol/tetrachloroethane (1/1 weight ratio) 100-
Measured at °C.

Affinity: The degree of affinity between particles and polymer was evaluated by the degree of void formation under certain conditions.

That is, an unoriented film with a thickness of 300μ was stretched 3.5 times in the longitudinal and transverse directions at 85°C, and the average length of the long and short axes of the particles in the film and the length of voids generated around the particles were calculated. The ratio between the average length of the axis and the short axis was determined. The arithmetic average of these values for each particle was determined and used as a measure of the affinity between the particles and the polymer. The larger this value is and the closer it is to 1, the fewer voids will occur and the better the affinity will be. The stretching conditions are 70
00%/ゝN. It was adopted. In addition, in Examples and Comparative Examples, “
"Parts" indicates "parts by weight."

Example 1 [Production of crosslinked polymer fine powder] A homogeneous solution of 100 parts of methyl methacrylate, 25 parts of divinylbenzene, 22 parts of ethylvinylbenzene, 1 part of benzoyl peroxide, and 100 parts of toluene was dispersed in 700 parts of water.

Next, the mixture was heated to 80° C. for 6 hours with stirring to carry out polymerization under a nitrogen atmosphere.

The average particle size of the resulting crosslinked polymer particles having ester groups was about 0.11.

The resulting polymer was washed with demineralized water and diluted with 500 parts of toluene.
The mixture was extracted twice to remove a small amount of unreacted monomer linear polymer. Next, the polymer particles were crushed with an attritor for 2 hours and with a sand grinder for 2 hours to obtain an average particle size of 2.
A crosslinked polymer fine powder of 0μ was obtained. [Manufacture of polyester film] 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.09 parts of calcium acetate hydrate
1 part was placed in a reactor, and 0.10 parts of the previously obtained fine polymer powder having an average particle size of 2.0 .mu.m was added thereto to carry out a transesterification reaction.

The reaction temperature was 165°C at the start of the reaction, 200°C after 2 hours, and 230°C after 2 hours. In order to confirm the reaction between the polymer fine powder and ethylene glycol, both were placed in a separate reactor at a molar ratio of 1/10 and kept at the boiling point of ethylene glycol for 2 hours to examine the distillate, and methanol was found. .

This was produced by the reaction between the methyl ester groups in the crosslinked polymer and ethylene glycol, and the amount thereof was approximately 5 mol % based on the total methyl ester groups. This amount was sufficient to react with most of the functional groups located on the surface layer of the crosslinked polymer. 4
After a period of time, 0.036 parts of phosphoric acid and 0.03 parts of antimony trioxide were added to the reaction mixture, in which the transesterification reaction had substantially completed, and polymerization was carried out according to a conventional method.

That is, the temperature was gradually raised from 230°C to 280°C.
On the other hand, the pressure gradually decreased from normal pressure and finally reached 0.5mmH9.
And so. After 4 hours, the polymer was discharged and formed into chips.

The intrinsic viscosity of this polymer was 0.66. Next, this polyester was melted at 290°C, extruded through a T-shaped die, rapidly cooled, stretched by 315 times in both the longitudinal and transverse directions, and then heat-treated at 190°C for 10 seconds to a thickness of 1.
It was made into a 1μ film.

The crystallinity of this film was 43%.
This film was evaluated as a film for magnetic tape, that is, its friction coefficient, abrasion resistance, and electromagnetic conversion characteristics were measured.

The results are shown below along with Examples 2 to 5 and Comparative Examples 1 to 7.
Shown in the table. Examples 2 and 3 A film with a thickness of 11 μm was obtained in the same manner as in Example 1, except that the average particle size and the amount added of the fine polymer powder were changed.

The measurement results for this film are shown in Table 1.

Example 4 The polymer particles having an ester group and having an average particle diameter of about 0.11 obtained in Example 1 were saponified.

Saponification was carried out using a 20% by weight aqueous sodium hydroxide solution.
The test was carried out at 80°C for 18 hours. Particles after reaction - Examination of this infrared absorption spectrum revealed that 1 is based on ester groups.
The absorption near 735C7ft-1 completely disappears and a new 17
Absorption based on carboxyl groups appeared near 00CWL-1. Next, this polymer granule is crushed to have an average particle size of 1.
A polymer 3 fine powder having a carboxyl group of 6μ was obtained. Separately, 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.09 parts of calcium acetate hydrate were placed in a reactor, and a transesterification reaction was carried out in the same manner as in Example 1.

After 4 hours, 0.036 parts of phosphoric acid and 0.15 parts of the previously obtained fine polymer powder having carboxyl groups with an average particle size of 1.6 μm were added to this reaction mixture in which the transesterification reaction was substantially completed. Further, 0.03 part of antimony trioxide was added and polymerization was carried out in the same manner as in Example 1 to obtain a polyester. Next, using this polyester, a polyethylene terephthalate film having a thickness of 11 μm and a crystallinity of 45% was obtained in the same manner as in Example 1.

The measurement results for this film are shown in Table 1. Example 5 A test was conducted using the edge of the film obtained during the film forming operation in Example 1 as a recycled product.

That is, the ends of the film obtained in Example 1 were melted again and pelletized, and then mixed with fresh chips of Example 1 of the same weight. Using this chip group containing half of the recycled products, a film was formed in the same manner as in Example 1 to obtain a polyethylene terephthalate film having a thickness of 11 μm and a crystallinity of 38%.

The measurement results for the obtained film are shown in Table 1.
. Comparative Example 1 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.12 parts of calcium acetate hydrate were placed in a reactor and a transesterification reaction was carried out.

After completion of the transesterification reaction, 0.03 part of antimony trioxide was added and a polyester containing precipitated particles of oligomeric calcium salt was obtained in accordance with a conventional method.

The diameter of the precipitated particles was approximately 2 to 3 microns. Next, using this polyester, a film was formed in the same manner as in Example 1 to obtain a polyester film having a thickness of 11 μm and a crystallinity of 42%. Table 1 shows the measurement results for the obtained film. Comparative Examples 2 to 4 A biaxially stretched polyester film having a thickness of 11 μm was obtained in the same manner as in Example 4 except that various inorganic compounds were added instead of the fine polymer powder.

Table 1 shows the measurement results for the obtained film.
Comparative Example 5 A test was conducted using the edge of the film obtained during the film forming operation in Comparative Example 1 as a recycled product.

That is, in Example 5, the film ends and chips of Comparative Example 1 were used instead of the film ends and chips of Example 1, and a polyester film containing half of the recycled product was obtained by the same operation as in Example 5. Table 1 shows the measurement results for the obtained film. Z1 Comparative Example 6 A film was obtained in the same manner as in Example 1 except that the average particle diameter of the fine polymer powder, the amount added, and the crystallinity of the film were changed.

The measurement results for this film are shown in Table 1.

As is clear from the results in Table 1, the polyester film containing a specific particle size and specific amount of the fine polymer powder of the present invention has good dispersibility of the particles and is excellent in slip properties and electromagnetic conversion properties. There is.

1. Furthermore, the film of the present invention has the characteristic that these characteristics are not lost even when it is used as a recycled product. On the other hand, when the precipitation method is adopted, although the electromagnetic characteristics are good, the generation of white powder A cannot be prevented, and the sliding property is further deteriorated.

This is a common defect that is observed when a certain amount or more of particles formed by the precipitation method are contained. Also, kaolin, calcium carbonate,... When an inorganic compound such as talc is added, although it is generally excellent in prevention of white powder generation and slipperiness, the particles tend to aggregate and form secondary particles, and deterioration of white powder B and electromagnetic conversion characteristics is unavoidable.

Example 6 A polyester obtained in the same manner as in Example 1 except that the amount of crosslinked polymer fine powder added was 0.2% by weight was melted at 290°C and extruded through a T-shaped die to give a thick The unoriented film was molded into a film with a diameter of 75 μm, and the unoriented film was
After stretching 3.5 times in the longitudinal and transverse directions at ~90°C, 2
Heat treatment was performed at 05° C. for 7 seconds to form a film with a thickness of 6 μm.

The crystallinity of this film was 48%. The evaluation results regarding the properties of this film as a capacitor film, that is, friction coefficient, electrical properties, ejection deformation resistance, and workability during slitting, are shown in Table 2 together with Examples 7 to 10 and Comparative Examples 7 to 11 below. show.

Examples 7 and 8 Example 6 except that the conditions shown in Table 2 were changed in Example 6.
A film with a thickness of 6 μm was obtained in the same manner as above.

The measurement results for this film are shown in Table 2. Example 9 Weakly acidic cation exchange resin WK-10 (manufactured by Mitsubishi Chemical Industries, Ltd., metatallylic acid-divinylbenzene copolymer)
A jet mill (PJMl manufactured by Nihon Niyuma Chitsuku Co., Ltd.)
The mixture was ground to an average particle size of 4 μm using a sand grinder to obtain a crosslinked polymer fine powder having a carboxyl group and an average particle size of 1.8 μm.

Next, in Example 4, a polyester containing the particles was prepared in the same manner as in Example 4, except that 0.18 parts of this fine polymer powder with an average particle size of 1.6 μm was used instead of 0.15 parts. I got it. Next, using this polyester, a polyester film having a thickness of 6 μm and a crystallinity of 48% was obtained in the same manner as in Example 6.

The measurement results for this film are shown in Table 2.

Example 10 A test was conducted using the edge of the film obtained during the film forming operation in Example 9 as a recycled product.

That is, the ends of the film obtained in Example 9 were melted again and pelletized, and then mixed with fresh chips of Example 9 of the same weight. Using this chip group containing half of the recycled products, a film was formed in the same manner as in Example 9 to obtain a polyester film with a thickness of 6 μm.

Table 2 shows the measurement results for the obtained film.
Comparative Example 7 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.09 part of calcium acetate hydrate were placed in a reactor and a transesterification reaction was carried out.

After completion of the transesterification reaction, 0.03 part of antimony dioxide was added and a polyester containing precipitated particles of oligomeric calcium salt was obtained in accordance with a conventional method. The diameter of the precipitated particles was approximately 5μ. Next, using this polyester, a film was formed in the same manner as in Example 6 to obtain a 6 μm thick polyester film.

Table 12 shows the measurement results for the obtained film. Comparative Examples 8 to 10 Example 9 except that the conditions shown in Table 2 in Example 9 were changed.
A polyester film having a thickness of 6 μm was obtained in the same manner as above.

Table 2 shows the results of nine measurements on the obtained film. Comparative Example 11 A test was conducted using the edge of the film obtained during the film forming operation in Comparative Example 7 as a recycled product.

That is, in Example 10, the film ends and chips of Comparative Example 7 were used instead of the film ends and chips of Example 9, and a polyester film containing half of the recycled product was obtained by the same operation as in Example 10.

Table 2 shows the measurement results for the obtained film.
As is clear from the results in Table 2, the polyester film containing the fine polymer powder of the present invention has good dispersibility of the particles and is excellent in friction coefficient and ejection deformation resistance.

Furthermore, the electrical properties represented by the dielectric strength and CR value are good, and these properties are not impaired even when recycled and used. On the other hand, when the precipitation method is adopted, although the electrical properties are comparable, the friction coefficient and resistance to protrusion deformation are inferior, and furthermore, when recycled and used, the slipperiness becomes even worse.

Additionally, when inorganic compounds such as kaolin, calcium carbonate, and talc are added, although they are generally excellent in terms of friction coefficient and anti-protrusion deformation properties, particles tend to aggregate and form secondary particles, and a decline in electrical properties is unavoidable. Example 11 Crosslinked polymer particles having an average particle size of about 0.211 were obtained in the same manner as in Example 1, except that 200 parts of methyl methacrylate was used instead of 100 parts of methyl methacrylate.

! Next, a crosslinked polymer fine powder having an average particle size of 1.8 μm was obtained in the same manner as in Example 1. Next, in the production of polyester in Example 1, 0.05 parts of the previously obtained fine polymer powder with an average particle size of 1.8 μm was used instead of 0.10 parts of the fine polymer powder with an average particle size of 2.0 μm. A polyester containing the fine polymer powder was obtained in the same manner as in Example 1.

Furthermore, a biaxially stretched polyester film having a thickness of 2.5 μm was obtained in the same manner as in Example 1.

About this film Polyester filament for vapor deposition 3! The following Example 12-13 and Comparative Example 12-1 show the results of evaluation as a lume, that is, the relationship between slipperiness and transparency, the difference between the front and back sides after aluminum vapor deposition, and the degree of thread breakage.
It is shown in Table 3 together with 4.

In addition, the affinity between the particles and polyester was also listed as an evaluation item. Examples 12 to 13 A film with a thickness of 25 μm was obtained in the same manner as in Example 11, except that the conditions shown in Table 3 were changed.

The measurement results for the film are shown in Table 3.

Comparative Example 12 A film with a thickness of 25 μm was obtained in the same manner as in Example 11 except that the timing of addition of the fine polymer powder was changed.

That is, a film was obtained by blending a crosslinked polymer fine powder with an average particle size of 1.8 μm with a polyester having an intrinsic viscosity of 0.65 after the completion of the polycondensation reaction and before film formation.

The measurement results for this film are shown in Table 3.

Comparative Examples 13 and 14 Films with a thickness of 25 μm were obtained in the same manner as in Example 11 using the polyesters obtained in Comparative Examples 1 and 4, respectively.

The measurement results for this film are shown in Table 3.

As is clear from the results in Table 3, the polyester film of the example satisfies all the characteristics, whereas the crosslinked polymer film of Comparative Example 12, which has a group capable of reacting with polyester, does not react with the crosslinked polymer. If the reaction time with polyester is short and there is little opportunity for reaction, that is, if the two are simply blended before film formation, the effects of the present invention cannot be expected, and the effects of the present invention may not be expected, resulting in poor dispersion, generation of voids, and furthermore, a decrease in transparency and thread breakage. This will lead to frequent occurrence. Moreover, it is difficult to satisfy all of these characteristics at the same time using conventionally known precipitation methods or addition methods as in Comparative Examples 13 and 14.

Claims (1)

[Claims] 1. Crosslinking degree of 8 to 50% obtained by copolymerization of a compound having only one aliphatic unsaturated bond in the molecule and a compound having two or more aliphatic unsaturated bonds in the molecule,
A polyester film comprising 0.001 to 4% by weight of a crosslinked polymer having an average particle size of 0.1 to 5 μm, and the polymer is substantially covalently bonded to the polyester.