JPH0231745B2 - JIKIKIROKUTAI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic recording medium with excellent adhesiveness between a magnetic layer and a biaxially oriented polyester film (hereinafter simply referred to as polyester film). Currently, magnetic recording materials generally used include those made by coating a polyester film with a magnetic paint made of a mixture of magnetic powder and a resin binder. When a polyester film is used as a base for a magnetic recording medium, one of the important properties is that the magnetic layer and the polyester film have excellent adhesion. Conventionally, attempts have been made to improve the adhesiveness of both magnetic paints and polyester films, but no suitable method of improvement has yet been found. The component that governs the adhesion to the polyester film in the magnetic paint is mainly the binder resin. As binder resins, vinyl resins, cellulose resins, urethane resins, epoxy resins, phenoxy resins, and the like are generally used. For example, among vinyl resins, vinyl chloride-vinyl acetate copolymer is used as the main binder resin for audio tapes, and polyurethane resins are used as the main binder resin for video tapes. Therefore, methods for improving magnetic coatings include changing the type of binder resin, using other resins as second and third components, and using additives and crosslinking agents. Many examples are known of attempts to improve adhesiveness with polyester films. However, the selection and formulation of the binder resin in the magnetic paint requires not only adhesion with the polyester film, but also dispersibility of the magnetic powder, high packing density,
Because it is required to satisfy various properties such as maintaining high coercive force, excellent electromagnetic conversion characteristics, and wear resistance of the magnetic layer during repeated running, it is necessary to use polymers that are mixed with the main binder resin. In addition to their own limitations, magnetic paint binders tend to be generally expensive in construction. On the other hand, as a method for improving adhesion from the polyester film side, for example, a method is known in which polyester contains polyalkylene glycol to improve adhesion with various binders (Japanese Unexamined Patent Publication No. 18872/1983, Publication No. 51-90346).
However, such a film is not a preferred method because the properties necessary for a base film for magnetic recording media, such as high strength, high Young's modulus, and low heat shrinkage, often deteriorate. Therefore, the present inventors conducted repeated studies to obtain a polyester film that has excellent adhesion to magnetic paint without impairing the inherent mechanical strength and thermal dimensional stability of polyester film, and as a result, the present invention was developed. It has been completed. That is, the present invention provides a magnetic recording material comprising a magnetic layer and a polyester film containing 0.05 to 10% by weight of a polyamide resin obtained from polymeric fatty acids and diamines and having a film density of 1.375 to 1.405 g/ ^cm3 . exists in The present invention will be explained in more detail. The polyester referred to in the present invention refers to a polyester obtained using terephthalic acid or its alkyl ester and ethylene glycol as main starting materials, but other third components may be used as part of the raw materials. The third component is an aromatic dicarboxylic acid component such as isophthalic acid, naphthalene dicarboxylic acid, or one or more of their alkyl esters, and a glycol component such as a polyalkylene such as propylene glycol tetramethylene glycol or polyethylene glycol. One kind or two or more kinds of glycols can be used. In any case, in the present invention, polyester refers to a polyester in which at least 80% of the repeating structural units are ethylene terephthalate units. The polyamide resins used in this invention are a family of polyamide resins made from polymeric fatty acids and various diamines. The polymer fatty acids referred to in the present invention are those synthesized by heating ethylenically unsaturated and acetylenically unsaturated fatty acids to high temperatures in the presence of peroxides, Lewis acids, Bronsted acids, etc.
Industrially, it is synthesized by thermal polymerization of tall oil fatty acids, which are mainly composed of linoleic acid and oleic acid, which are easily available and easy to polymerize. Polymeric fatty acids are generally obtained as a mixture of unreacted monomeric fatty acids, dimerized fatty acids, and trimerized fatty acids, and are subjected to vacuum distillation as necessary to adjust the composition to a constant ratio. A typical analysis example of commercially available polymeric fatty acids is monomeric fatty acid 0.5
to 5% by weight, dimerized fatty acids 75 to 83% by weight,
Trimerized fatty acids are 15-22% by weight. Commonly used diamines are aliphatic, cycloaliphatic or aromatic diamines. Specific examples of these diamine compounds include ethylenediamine, 1,
2-diaminopropane, 1,2-diaminobutane, 1,3-diaminopropane, 1,3-diaminobutane, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, decamethylenediamine, octadecamethylenediamine,
meta-xylene diamine, para-xylene diamine,
Examples include cyclohexylene diamine, bis(aminoethyl)benzene, bis(aminomethyl)cyclohexane, bis(aminoethyl)cyclohexane, methylenebisaminocyclohexane, and methylenedianiline. These diamines can be used singly or as a mixture of two or more. In the present invention, alkylene diamines having 2 to 6 carbon atoms are suitable as diamines. In the present invention, the polyamide resin may contain an acid component in addition to the polymeric fatty acid. The compound serving as the acid component is preferably an aliphatic, alicyclic or aromatic dicarboxylic acid. Examples of such acids include adipic acid, sebacic acid, succinic acid, glutaric acid, isophthalic acid, terephthalic acid, and phthalic acid. The polyamide resin used in the present invention contains an acid component mainly composed of these polymeric fatty acids and a diamine component.
It is produced by reacting at a temperature of 100 to 300°C while removing the reaction water (or removing the alcohol if an ester is used). This reaction is preferably carried out between 150 and 300°C.
It is carried out between 200 and 250°C. The reaction time is related to the temperature and requires 3 to 8 hours after reaching the specified temperature, but heating for too long is undesirable as it may cause deterioration of the polyamide resin, so a typical example of reaction conditions is 4 hours at 220°C. That's about it. Generally, the reaction is carried out under an inert gas atmosphere such as nitrogen to prevent decomposition due to contact with air during heating, and at the end of the reaction, the reaction system is evacuated to completely remove volatile components. Sometimes. In the polyamide resin used in the present invention, the mixing ratio of the basic raw material reactants is kept equal to the total acid equivalent and total amine equivalent, but when considering the presence of evaporated components during the reaction, an appropriate difference is required. It doesn't matter if there is. The polyamide resin used in the present invention is preferably terminal-capped with a monomeric aliphatic monocarboxylic acid having 2 to 22 carbon atoms as a chain-terminating component. A polyamide resin whose terminal end is capped with a monocarboxylic acid is desirable because it has less influence on the decrease in thermal stability of polyethylene terephthalate. The molecular weight of the polyamide resin used in the present invention is not particularly limited, but is preferably less than 30,000.
If it exceeds 30,000, it is not preferable because it often changes the surface morphology of the film. In the present invention, the amount of polyamide resin added from the polymer fatty acid blended and dispersed in the polyester film is preferably 0.05 to 10% by weight.
It is 0.1 to 8% by weight. If the amount of polyamide resin added exceeds 10% by weight, the mechanical properties and thermal properties of the polyester film will be impaired, which is not preferable. If it is less than 0.05% by weight, the effect of improving adhesion is insufficient. In producing the polyester film of the present invention, the polyamide resin is preferably added at a stage after producing the polyester resin and before extrusion molding. For example, it can be directly dispersed and mixed into the polyester resin before extrusion molding, or a high-concentration masterbatch resin can be prepared in advance, and this and the polyester homopolymer can be diluted and mixed to a predetermined concentration, and then extrusion molded. It is also possible to adopt a method of making a film using the same method. In addition to the kneading method, it is also possible to produce a high-concentration masterbatch resin by adding the resin after the polycondensation reaction is completed, for example. The method for producing the polyester film of the present invention is not particularly limited, but it is melt-extruded into a film at 270 to 295°C by a normal polyester film forming method, such as a T-die method or an I-die method, and then formed into an amorphous film. After forming a sheet, methods such as sequential biaxial stretching or simultaneous biaxial stretching in the longitudinal and transverse directions and heat treatment at a predetermined temperature can be adopted. The biaxially oriented polyester film of the present invention has a density in the range of 1.375 to 1.405 g/cm ³ . When the density is lower than 1.375 g/cm ³ , the resulting polyester film has poor thermal properties and is not preferred. On the other hand, if the density exceeds 1.405 g/cm ³ , the mechanical properties will drop significantly, which is undesirable. To make the film density in the range of 1.375 to 1.405 g/ ^cm3 , the biaxially stretched film is usually
Heat fixation may be carried out within a temperature range of °C. The magnetic paint according to the present invention means a paint in which, in addition to magnetic powder and a binder resin, a plasticizer, a lubricant, a dispersant, an antistatic agent, etc. are mixed and dispersed as necessary. Binder resins include the vinyl resins, cellulose resins, urethane resins, epoxy resins, and phenoxy resins listed above.
In particular, the polyester film of the present invention is effective for magnetic paints for video tapes that use urethane resin as the main binder resin. The thickness of the polyester film of the present invention is not particularly limited, but is preferably in the range of 5 to 30 microns. The polyester film of the present invention exhibits excellent adhesion with magnetic paint, but if necessary, it may be pretreated with ultraviolet irradiation, electron beam irradiation, corona discharge treatment, plasma or arc treatment before applying the magnetic paint. Discharge treatment, other surface treatments, etc. may also be applied. Next, a prepared magnetic paint is applied onto the polyester film by a known method (for example, JP-A-52-43405), and then dried and aged to form a magnetic layer. The magnetic paint is made of, for example, magnetic powder, especially γ-Fe ₂ O ₃ or cobalt-doped powder, a binder resin, and optionally additives such as a dispersant, lubricant, and antistatic agent. It is prepared by mixing, blending, and further adding an appropriate solvent. The coating thickness of the magnetic layer is approximately 5 μm after drying. The magnetic recording material thus obtained has excellent adhesion between the magnetic layer and the polyester film, does not impair the original physical properties of the polyester film, and is suitably used as a magnetic recording material for audio, video, etc. The present invention will be explained in more detail below with reference to Examples. Note that parts and % in the examples indicate parts by weight and % by weight, respectively. The methods for measuring and evaluating the main characteristics in the present invention are shown below. 1 Adhesive strength between magnetic layer and basic film Paste double-sided adhesive tape on a 1 mm thick stainless steel plate, and paste the magnetic recording material on top of it so that the magnetic layer surface of the magnetic recording material is in contact with the adhesive tape. . After that, the peel resistance force when peeling the polyester film at an angle of 180 degrees from the magnetic layer was measured using a tensile tester at 1000 mm/
Measure at a speed of min. Adhesive strength was expressed as a relative ratio to the adhesive strength of films obtained from polyethylene terephthalate homopolymer. 2 Tensile test Toyo Baldwin Tensilon UTM-
Using a mold, length 50 at 20℃ and 65% humidity.
A sample film with a width of 6.25 mm and a width of 6.25 mm was pulled at a speed of 50 mm/min, and the load during the 5% elongation period was taken as the _F5 value. Also, the slope of the initial tangent of the stress-strain curve is set to 1
Young's modulus was calculated based on % elongation. 3 Density: 25 in a mixture of n-heptane and carbon tetrachloride
This is a value measured using the float-sink method at °C. Example 1 Approximately 83% dimer acid and 17% trimer acid produced by thermal polymerization of tall oil fatty acids as acid components
A polyamide resin with a molecular weight of about 5200 and a softening point of 114°C, which is manufactured from a polymeric fatty acid consisting of a polymeric fatty acid, ethylenediamine as a diamine component, and stearic acid as an end-blocking fatty acid monocarboxylic acid component, is made into a polyethylene terephthalate resin by the method described below. It was made to contain. That is, 90 parts of polyethylene terephthalate resin that had been vacuum dried at 165°C for 6 hours was added to 60°C.
10 parts of the above polyamide resin vacuum-dried for 6 hours were blended, dry blended, and then extruded and kneaded at 290°C to obtain a masterbatch resin containing 10% polyamide resin. Next, 10 parts of the masterbatch resin and 90 parts of polyethylene terephthalate resin were dry blended, extruded through a T-die, rapidly cooled, stretched 4 times in the machine direction and 3.5 times in the cross direction, and then stretched at 220°C for 10 seconds. A biaxially oriented polyester film having a thickness of 15 μm was obtained by heat treatment. The density of this film was 1.390. For comparison, a biaxially oriented film made of polyethylene terephthalate homopolymer was obtained in the same manner. Magnetic paint was applied onto these films by the method shown below. (Preparation and application of magnetic paint) γ-Fe ₃ O ₃ 233 parts Polyurethane resin 50 parts Nitrocellulose 20 parts Polyvinyl chloride-vinyl acetate copolymer 30 parts Methyl ethyl ketone 900 parts The above components were stirred and mixed together in a ball mill for 40 hours. After dispersion, 15 parts of isocyanate was added and ball milling was further performed for 20 minutes to obtain a magnetic paint. This magnetic paint was applied onto the previously prepared biaxially oriented polyester film using a coater so that the dry film thickness was approximately 5μ, dried at 80°C for 1 minute, and then aged at 80°C for 40 hours. did. Thereafter, this coated film was cut into a width of 12.7 mm along the coating direction and used for measuring adhesive strength. The results are shown in Table 1. Examples 2-5 All of the following examples used polymeric fatty acids made from tall oil fatty acids. Further, the film forming method was carried out under the same conditions as in Example 1. Molecular weight produced using 1,3-diaminopropane as a diamine component and stearic acid as a monofunctional aliphatic carboxylic acid compound
Example 2 is an example of a biaxially oriented film containing 0.5% of the polyamide resin in polyethylene terephthalate in the same manner as in Example 1 using a polyamide resin having a softening point of 3200°C and 95°C. In Example 3, 1,4-
A polyamide resin having a molecular weight of 4500 and a softening point of 146°C, which was produced using bis(β-aminoethyl)cyclohexane as a monofunctional aliphatic carboxylic acid and oleic acid as a raw material, was mixed in polyethylene terephthalate in the same manner as in Example 1. An example of a biaxially oriented film containing 0.3% of is shown. Furthermore, as a diamine component, ethylene diamine and propylene diamine were used together (in a molar ratio of 3:
1) Example 4 is an example of a polyester film containing 0.7% of a polyamide resin having a molecular weight of 4500 and a softening point of 102°C, which was obtained by reacting a polymeric fatty acid at an acid to amine ratio of 1.02. In Example 5, sebacic acid (in an equivalent ratio to the polymer fatty acid) was added as an acid component to the polymer fatty acid.
0.6) and 1,4-bis(β
A polyamide resin with a molecular weight of about 7200 and a softening point of 192°C obtained by reacting with (aminoethyl)benzene and stearic acid as a monofunctional end-blocking agent was added to polyethylene terephthalate in an amount of 1.2% in the same manner as in Example 1. An example of a polyester film made using this method is shown below. The results are shown in Table 1. 【table】

Claims (1)

[Claims] 1. A magnetic recording material comprising a magnetic layer and a polyester film containing 0.05 to 10% by weight of a polyamide resin obtained from a polymeric fatty acid and diamines and having a film density of 1.375 to 1.405 g/cm ³ .