JPS5885926A - Film for magnetic recording tape - Google Patents

Abstract

PURPOSE:To obtain a composite film for magnetic recording tapes having excellent traveling characteristic by using polyester having metallic bases of sulfonic acids. CONSTITUTION:Terephthalic acid type polyester contg. 0.01-2.5mol% metallic bases of sulfonic acids based on the dibasic components in the entire polyester constituting unit or a mixture of said polyester and terephthalic acid type polyester contg. no metallic bases of sulfonic acids and terephthalic acid type polyester, contg. metallic bases of sulfonic acids dispersed with inert fine particles are combined in two layers and thereafter are melt-extruded to a film shape, an electric field is applied upon said composite film to apply electrostatic charge thereto and further the film is brought into tight contact with grounded cooling metallic bodies to cool and solidify the same, whereby the polyester film for magnetic recording tapes of 0.02-0.5mu surface roughness of the layer contg. the inert particles is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyester film for obtaining a magnetic recording tape having good running properties and good magnetic properties.

It is well known that two-wheel stretched polyester film is suitable as a base film for magnetic recording tapes, and in order to obtain a good magnetic recording tape, k is 1. The film surface for coating the magnetic recording layer must have good smoothness. On the other hand, it is also known that it is desirable for the nonmagnetic layer of the tape to have an appropriate level of roughness. When the surface to which the magnetic recording layer is coated has good smoothness, it becomes possible to coat the magnetic recording layer thinly and uniformly, and the electromagnetic conversion characteristics and dots and bumps are reduced. On the other hand, if one non-magnetic surface has a moderate roughness, Ki
The t-tape has better lubricity, and its runnability and durability are improved. In order to obtain a polyester film with different roughness on each surface, two types of polyester arms having different particle sizes or different particle contents of inert fine particles are composited,
A method of two-wheel stretching is known. Methods for combining two types of polyester resins include a method in which two types of ester resins are combined into two layers in a molten state inside a die or outside a die, and one is co-extruded, or one is extruded after extruding one type of polyester resin. A method is known in which another type of polyester resin is laminated in a molten state on a sheet obtained by cooling or stretching after cooling. A magnetic recording tape in which a magnetic layer is coated on the smooth side of polyester films having different surface roughnesses thus obtained is also already known.

Furthermore, it is known that when such a polyester/%' film is axially stretched and then re-stretched in the -axial or biaxial direction, distortion is less likely to occur in the magnetic recording layer.

On the other hand, in order to obtain a good magnetic recording tape, it is desirable that the surface roughness be appropriately adjusted and that there be little variation in film thickness. In order to reduce film thickness fluctuations, it is necessary to uniformly cool the molten sheet extruded from one die with a cooling drum and to uniformly stretch it, and to apply an electric field to the molten sheet to remove static charges. The electrostatic pinning method is mainly used to apply and adhere uniformly to the bonded cooling drum. In order to design polyester 11m that can be used in the electrostatic pinning method, it is known to add 41CFi, for example, an alkali metal compound or a mineral alkaline earth metal compound and a phosphorus compound in special proportions. . It is also known that if the amount of these compounds added in order to adjust the electrostatic pinning characteristics is increased, the internal particle diameter and particles will change and the surface roughness will change. On the other hand, when a tertiary compound is added to adjust the size and number of internal particles, the electrostatic pinning properties are seriously impaired. Furthermore, even when the surface roughness is adjusted using external particles, the electrostatic pinning characteristics change depending on the order in which they are added. As described above, the reality is that it is cumbersome to separately perform KIRK on the electrostatic binder characteristics and the surface roughness of the film, and requires special techniques.

As a result of intensive research into a method for separately determining electrostatic pinning characteristics and surface roughness, the present inventor found that
Just in case we arrived at this invention. That is, a method has been discovered in which electrostatic binning properties are imparted by bonding a sulfonated metal base into polyester molecules, while surface roughness is adjusted by internal particles and/or external particles. When a sulfonic acid metal base is bonded to a polyester molecule, electrostatic pinning properties can be imparted to the surface roughness of the polyester. , ff1m can now be easily obtained. By providing a magnetic layer on the smooth side of the polyester film thus obtained, a magnetic recording tape having good magnetic properties and good running properties can be obtained.

The polyester with a sulfonic acid metal base bonded to it as described in this JA refers to a) polyester-forming monomer having a sulfonic acid metal base as one type of acidic acid-based ester component unit. , 0.01 to 0.01 based on the dibasic acid component in all structural units of terephthalic acid type & 9 esters
Z, 6 mol-containing terephthalic acid polyester, or (
→ Polyester containing sulfonic acid metal base and sulfone II! & mono-terephthalic acid-based polyester containing no group bases, the content of sulfonic acid metal bases is 0.01 to 2.0% based on the dibasic acid component in all polyester structural units.
Refers to a mixture of terephthalic acid-based polyester that has been mixed to a concentration of 6 mol%. What is terephthalic acid polyester?1
It is a polyester consisting essentially of terephthalic acid residues and ethylene glycol residues, and other copolymerized components include isophthalic acid, 2,6-7thalenedicarponic acid, adipic acid, azelaic acid, cepacic acid, Dibasic acids such as dodecanedicarboxylic acid, glycols such as pyrene glycol, butanediol, neopentyl glycol, cyclohexane dimetatool 1 polyethylene glycol, polypropylene glycol, pritetramethylene glycol, or oxycarpenic acids such as hydroxybenzoic acid. etc. are used.

Examples of the above-mentioned polyester-forming monomer having a sulfonic acid metal group include the following.

80, M As the metal M of the above metal sulfonic acid salt, an alkali metal is preferably used, and lithium, sodium, potassium, etc. are used.

The polyester containing the above-mentioned sulfonic acid metal base in the W acid unit is an ester that does not have a dibasic acid component having a sulfonic acid metal base, an oxycarboxylic acid component, or a multi-component, and a sulfonic acid metal base. Esterification or transesterification with the forming component in the presence of a catalyst,
Obtained by polycondensation reaction under vacuum.

The amount of the sulfonic acid metal base contained in the terephthalic acid polyester of the present invention is preferably 0.01 to 2.15 molar based on the dibasic acid component in all polyester structural units, and preferably 1i o, oa ~1 mil 1 mole.

If the amount of the sulfonic acid metal base is less than 0.02 moA/s, the adhesion to the surface of the cooling body is insufficient and the desired effect cannot be obtained. In addition, if the concentration is 2.5 molar or more, insoluble substances will be generated and the surface roughness of the S film will increase. A &IJ ester containing no inert particles and a polyester containing inert particles are prepared. Surprisingly, it is an original invention that the electrostatic pinning characteristics are not affected by the presence or absence of inert particles, the type, amount, and timing of addition of inert particles. The thus obtained ester substantially free of inert particles and the polyester containing inert particles are composited into two layers and subjected to melt extrusion into a film, and an electric field is applied to the film to remove the static charge. After that, the film is brought into close contact with a grounded cooling metal body.
The inert fine particles mentioned in the present invention refer to inorganic particles that are substantially inert to polyester, and may be either internal particles or external particles. Internal particles and particles added during polyester synthesis/polymerization and participating in esterification, transesterification or polycondensation reactions, inorganic fine particles produced after these reactions, and IJ ester monomers. Refers to inorganic salt fine particles that chemically react with polymers and agglomerate and grow during polymerization. Examples include bird alkali metal compounds, alkaline earth metal compounds, antimony trioxide, germanium compounds, titanium compounds, and phosphorus compounds. On the other hand, it refers to inert fine particles that are added during the synthesis and polymerization of the external particles and polyester described in the present invention or after the polymerization and do not participate in the chemical reaction. , silica, talc, titanium dioxide, calcium carbonate, etc.

These fine particles may be used alone as internal particles or external particles, or both may be used, but the particle size and amount of addition are determined after melt extruding polyester and two-wheel stretching. The surface roughness of the surface that becomes the first rough surface after re-stretching in the axial or two-wheel direction is O, O, a~o, 51
It is adjusted so that tl/C, but specifically the particle size is 0.
．． It is adjusted so that 0.01 to 1 weight of fine particles of 2 to 5 μm is contained. The polyester bonded with the metal sulfonate base described in the present invention has the characteristic that the electrostatic pinning properties are virtually unaffected by the order of addition or timing of addition when external particles are added or when internal particles are formed. In addition to this, the particles have good dispersibility in the polyester used in the present invention, and a uniform rough surface can be obtained. The surface roughness described in the present invention is measured by a stylus type surface roughness needle defined by 1J Eng. 8-1806!11 and is expressed as center line average roughness defined by S': JXB-BO601. On the other hand, the surface roughness of a smooth surface is substantially less than 0.02 μ, which makes it possible to make the magnetic layer coated thereon thin and uniform, resulting in magnetic recording properties.ゎImprovement. Rough surface. Roughness, expressed. ,. When the surface roughness is set to t~1.0μ, the running properties of the tape become better, but if the surface roughness exceeds 1.0μ, the magnetic layer may get stuck when the tape is wound up, even if it gets caught during running. , an uneven transfer occurs. Surface roughness is 0. O
If it is below la p, the running properties of the tape will deteriorate, and
This will cause trouble in the magnetic layer coating process.

The basic embodiments of the present invention will be explained below with reference to Examples.

(Manufacture of polyester) After esterifying terephthalic acid and ethylene glyfur, 1,3-dihydroxyethyl-5-alkalisulfonoxyisoheptatarate was added as a polymerization catalyst to an antimony trioxide to sulfone metal salt compound. In addition, a copolymerized polyester was obtained by carrying out paper-making condensation using a conventional method. Select I&SIC as the alkali metal of the sulfonic acid metal salt.
Polycondensation was carried out by changing the amount of the sulfonic acid kinkoshi salt compound.

As another example, a copolymerized polyester containing a large amount of the metal sulfonate compound was produced and mixed with a polyester not containing the metal salt to obtain polyester compositions containing varying amounts of the metal sulfonate.

In addition, various inert particles may be added or generated during or after esterification of terephthalic acid and ethylene glycol, prior to polycondensation, or during the process of proceeding with polycondensation. A meliester composition containing at least inert particles was obtained.

As another example, in a method of esterifying terephthalic acid and ethylene glycol and then polycondensing them (using an antimony trioxide catalyst), 0.1% by weight of calcium acetate and 0.075% by weight of trimethyl phosphate are added,
A comparative polyester was also obtained by adding inert particles.

(Method of If Exhibition) The above polyester not containing inert particles and the polyester containing inert particles are each melt-extruded at 890°C using an extruder with a diameter of 90-1 and a gow, and the two layers are composited in a die. After making it as one body, 5ocWc
Dispense onto a cooled metal rotating drum and allow it to cool and solidify. Besides this, in order to bring the sheet material into close contact with the cooling drum using the electrostatic pinning method, a nichrome wire electrode with a diameter of 0.3 mm was placed at the reaction position and connected to the rotating drum through the sheet material. 1 between the cooling drum
A high voltage of 0 to 1 tKV was applied. The total thickness of the sheet material was 150 μm, and the thickness ratio of the smooth surface layer to the rough surface waste was adjusted to be 60:40.

This sheet was heated to 11cB in the longitudinal direction at a temperature of 85 to 90℃, and
Stretch it twice and stretch it to 911. , B at a temperature of -13!1℃, after stretching 5 times, heat setting at 200℃ to a thickness of 18μ
A polyethylenetere-7-talate composite film was obtained.

(Evaluation method) (1) Electrostatic pinning characteristics Polyester is extruded onto a cooling roll while a high voltage is applied. First, the speed is increased to soil removal, and the cooling pinning
- The maximum speed (adherence limit speed) at which air is trapped between the seal and the seal and air bubbles begin to enter is taken as a measure.

(2) Roughness of film The surface roughness was measured using a sur-7-5 manufactured by Tokyo Seimitsu Department Co., Ltd., and the center line average roughness was determined.

Example L A polyester was prepared by copolymerizing a sulfonic acid sodium salt compound with 0.5 moles of the dibasic acid component in all the polyester structural units. At any stage in the polymerization of this polyester, kaolin with an average particle size of 0.8 μm is added in the form of a slurry of KS ethylene glyfur to give an O,S weight percent of the polyester containing inert particles. Then, the polymerization was carried out.

Regarding the polyester thus obtained, the adhesion limit speed in electrostatic pinning was investigated. The results are listed in Table 1. As a comparison, a polyester with added calcium acetate and trimethyl phosphate was polymerized according to known techniques for imparting electrostatic pinning properties, and at any stage of the polymerization 0.3% of the kaolin described in Example 1 was added. The adhesion limit speed was also determined for those added by weight.

Furthermore, as a comparison, lithium acetate was added to polyester to which calcium acetate and trimethyl phosphate were added for the purpose of generating an internal lubricant, and polyester containing OS acid metal salt showed superior results regardless of the timing of addition of inert particles. This shows the electrostatic pinning characteristics. On the other hand, when imparting electrostatic pinning properties with calcium and compounds, the electrostatic pinning properties change depending on the timing of addition of ore and inert particles. Needless to say, when the adhesion limit speed is low, the production speed of the Ks film must be reduced in order to ensure the quality of the S film.

Example While performing electrostatic pinning from two kinds of polyesters, sample number 1 and sample number 30 listed in Table 1,
Melt extrusion was carried out at a speed of s+ys/min and biaxially stretched to obtain a composite polyester film tube consisting of layers).

For comparison, sample number 6 and sample number 7 were made from polyester of 2 ms and subjected to electrostatic pinning and oil-melt extrusion at Iθ. The speed was fix'y+a1 minute, which enabled continuous and stable operation.

The surface roughness of these am@ films is shown in Figure 1, and it is clear that polyester containing sulfone sheet metal salt has good dispersibility of 1 inert particles and does not exhibit abnormally large surface protrusions. .

Table 1 Polyester polymerization method and adhesion limit speed

[Brief explanation of the drawing]

The first gl represents the surface roughness of the composite film. Patent Applicant Toyobo Co., Ltd. Procedural Amendment 1 Description of the Case 1982 Patent Application No. 182904 Title of the invention Film screw for magnetic recording tape Person making the amendment Relationship to the case Patent Applicant 2-chome Dojimahama, Kita-ku, Osaka Detailed Description of the Invention and Scope of Claims in Specification No. 2 No. 8 Contents of amendment (2) Correct “soil removal” to “gradually” in line 1O, page 13 of the same (8) On page 14, line 7, "I investigated." is corrected to "I investigated (sample number x-4)." (4) Correct "solid." in line 14 of page 1 to "solid (sample numbers 5 to 8) o." (5) On page 14, line 19, "I investigated." is corrected to "I investigated (sample number 9)." (6) Add the following data to the bottom of the table in "Table 1" on page 16. (Note) 0.05% of lithium acetate was added when preparing raw materials for the purpose of generating extremely rich internal particles. "another
Paper Patent Claims A terephthalic acid polyester in which a sulfonic acid metal base is bonded in the molecule, or a mixture of the polyester and a terephthalic acid polyester that does not have a sulfonic acid metal base, in which the total amount of the sulfonic acid metal base is 0.01 to 2.5 based on the dibasic acid component in the polyester structural unit
One layer of terephthalic acid-based polyester adjusted to a molar ratio is bound 1 The other layer is a layer of polyester in which inert fine particles are dispersed in the polyester 1 These two layers are made into a composite film, and then an electrostatic charge is applied to the composite film. While applying the inert particles, the layer is melt-extruded onto a grounded cooling metal roll, cooled and solidified, and stretched in at least the z-axis direction to give a surface roughness of 1 inert particles of o, og to 0. Polyester film for magnetic recording tape characterized by having a thickness of 5 μ 〇 Procedural amendment (method) % formula % L Case description 1982 Patent Application No. 182904i Name of the invention Magnetic recording tape film & correction Relationship with the case Patent applicant 2-2-8 Dojimahama, Kita-ku, Osaka (316) Toyobo Co., Ltd. Date of March 1981 Subject of amendment (2) Page 16 of the specification, simple drawings The explanation is corrected as follows.

Claims (1)

[Claims] A terephthalic acid polyester that has a sulfonic acid metal base bonded to the molecule, or a mixture of the same polyester and a terephthalic acid polyester that does not have a sulfonic acid metal base, can be used to determine the amount of the sulfonic acid metal base in the total polyester structural unit. Based on the dibasic acid component in c site o, ox-1!
,! One layer is made of terephthalic acid polyester prepared in I-r-*%6C1pl, and the other layer is made of polyester in which inert fine particles are dispersed in the polyester, and these eight layers are made into a composite film, and then the composite film is While applying an electrostatic charge to the layer, it is melt-extruded onto a grounded cooling metal roll, cooled and solidified, and then stretched in at least 8 axial directions to reduce the surface roughness of the layer containing 1 inert particles to 0.
．． 1. A polyester film for magnetic recording tape, characterized in that it has a molecular weight of 02 to O, aμ.・