JPH01184629A - Production of resin for magnetic coating compound - Google Patents

Abstract

PURPOSE:To enhance durability and to prevent degradation in characteristics after long-term use by bringing a monoester phosphate compd. into reaction with a vinyl chloride resin having an epoxy group, thereby satisfactorily dispersing magnetic powder. CONSTITUTION:The vinyl chloride resin having the epoxy group is obtd. by a method for polymerizing vinyl chloride, radical-polymerizable monomer having the epoxy group which can be copolymerized with the vinyl chloride and if necessary, a polymer which can be copolymerized with these monomers in the presence of a radical generator or a method for epoxylating the resin which is partially dehydrochlorinated by heating of a copolymer resin essentially consisting of polyvinyl chloride or contact with a dehydrochlorinating agent by an epoxylating agent such as percarboxylic acid, etc. The vinyl chloride resin contg. the phosphoric acid group obtd. by copolymerizing the phosphoric acid group-contg. monomer and the -X-OH group (X is an org. residue)-contg. monomer with the vinyl chloride and -X-OH, therefore, acts usefully as a resin binder.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a resin for magnetic coating material for producing magnetic recording media having excellent magnetic particle dispersibility.

(Prior Art) Magnetic recording media such as magnetic tapes and magnetic cards are generally manufactured by applying a magnetic paint containing magnetic powder and its binder as a magnetic layer onto a substrate such as a polyester film. In recent years, in order to increase coercive force and maximum saturation magnetization, and improve S/N ratio and recording density, finer magnetic powders with larger coercive force (larger specific surface area) than the above-mentioned magnetic powders have been used. It has become.

However, as a binder for such fine magnetic powder, vinyl chloride-vinyl acetate-vinyl alcohol copolymer resin, vinyl chloride-vinyl acetate-maleic acid copolymer resin, vinyl chloride-vinyl acetate-maleic acid-vinyl alcohol copolymer resin When a magnetic paint is prepared using a vinyl chloride copolymer resin such as a resin, there are problems such as thickening of the paint and insufficient dispersibility. In addition, low molecular weight surfactants are used as dispersants to improve dispersibility, but if large amounts of these dispersants are used, they may reduce the durability of the magnetic recording medium.
There is naturally a limit to the amount that can be used because it causes head stains and the like.

On the other hand, in order to improve the durability and reliability of magnetic recording media,
A crosslinking agent that reacts with a part or all of a flexible material such as polyurethane resin, polyester resin, acrylonitrile-butadiene rubber, and a binder to form a crosslinking bond is added to the magnetic paint to form a crosslinked magnetic layer. What you can do is
This is a common method especially for magnetic recording tapes. Therefore, the binder is required to be compatible with these flexible materials and to have appropriate reactivity with the crosslinking agent. Furthermore, in order to improve tape reliability, tapes are increasingly required to have excellent chemical stability and to be less likely to generate decomposition products that can cause deterioration of magnetic powder or corrosion of heads. It's coming.

In order to improve the performance of such magnetic recording media, it has been reported that a magnetic paint having excellent magnetic powder dispersibility can be obtained by using a resin having a phosphoric acid group as a binder. (Chemistry and Industry 61(5), 173 (
19B? ) Chubu et al.) Therefore, by introducing a phosphorus M group into vinyl chloride resin, which has excellent physical properties as a binder for magnetic recording media, magnetic recording media with good electromagnetic conversion properties and excellent durability can be obtained. For example, a method of reacting a part of the hydroxyl groups of a vinyl chloride-vinyl acetate-vinyl alcohol terpolymer with a chloride or isocyanate compound containing a phosphoric acid group ( JP-A-57-44227), a method of converting the hydroxyl group of a vinyl chloride-vinyl acetate-vinyl alcohol terpolymer into a phosphoric acid ester using phosphoric anhydride, etc. (JP-A-57-44227);
-172214) are introduced. However, in all of these methods, unreacted raw materials, reaction by-products, and even the reaction medium have a negative effect on the durability and dispersibility of the magnetic recording medium, so these must be carefully removed in the post-reaction process. In addition, the vinyl chloride resin tends to deteriorate in the process of these modification reactions, resulting in a decrease in the durability of the magnetic recording medium.

(Problems to be Solved by the Invention) One of the inventors of the present invention previously proposed a vinyl chloride resin binder having excellent magnetic particle dispersibility and durability and having a phosphoric acid group and a hydroxyl group, which does not have the above-mentioned drawbacks. Phosphate group-containing monomer and -
A phosphoric acid group obtained by copolymerizing a monomer containing an X-011 group (X is an organic residue) with vinyl chloride and -
It has been discovered that a vinyl chloride resin containing It is an object of the present invention to obtain a vinyl chloride resin for paints by a method that does not involve polymerization and does not have the drawbacks of the prior art described above. This is achieved by reacting.

The vinyl chloride resin having an epoxy group used in the present invention is composed of (1) vinyl chloride, a radical polymerizable polymer having an epoxy group that can be copolymerized with vinyl chloride, and if necessary copolymerizing with these monomers. (2) Partial dehydrochlorination of polyvinyl chloride or a copolymer resin containing vinyl chloride as a main component by heating or contacting with a dehydrochlorination agent. It can be obtained by epoxidizing a resin treated with hydrogen chloride using an epoxidizing agent such as percarboxylic acid. The chlorinated polyvinyl chloride resin having an epoxy group can be obtained by the method (2) using a chlorinated polyvinyl chloride resin or a chlorinated polyvinyl chloride copolymer resin as a starting material.

Examples of monomers having epoxy groups used in the production of vinyl chloride resins having epoxy groups include glycidyl ethers of unsaturated alcohols such as allyl glycidyl ether and methallyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate, Glycidyl
Glycidyl esters of unsaturated acids such as p-vinyl benzoate, methylglycidyl itaconate, glycidyl ethyl maleate, glycidyl vinyl sulfonate, glycidyl (meth)allylsulfonate, pucdiene monooxide, vinylcyclohexene monooxide, 2-
Examples include epoxide olefins such as methyl-5,6-epoxyhexene.

In addition, examples of monomers having an epoxy group and monomers used as necessary other than vinyl chloride include carboxylic acid vinyl esters such as vinyl acetate and vinyl propionate; methyl vinyl ether, isobutyl vinyl ether;
Vinyl ethers such as cetyl vinyl ether, vinylidene chloride, vinylidene fluoride, etc.: diethyl maleate, butyl benzyl maleate, di-2-hydroxyethyl maleate, dimethyl itaconate, methyl (meth)acrylate, (meth)acrylic acid Unsaturated carboxylic acid esters such as ethyl, lauryl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate; Olefins such as ethylene and propylene; Unsaturated nitriles such as (meth)acrylonitrile; Styrene, α-methylstyrene and aromatic vinyl such as p-methylstyrene. These monomers are used not only to improve the solubility of the resin by controlling the compatibility and softening point of the resin of the present invention and other resins when mixed, but also to improve the properties of the coating film and the coating properties. Appropriate selection is made depending on the need for process improvement, etc.

The weight fraction of epoxy groups in the vinyl chloride resin in the present invention is preferably in the range of 0.3 to 20% by weight; if it is less than 0.3% by weight, it is difficult to achieve the purpose of the present invention (20% by weight).
When the amount is larger, the amount of vinyl chloride is relatively reduced, and the physical properties of the resin are deteriorated. The proportion of vinyl chloride in this resin is usually 50% by weight or more, preferably 70 to 95% by weight.

If the ratio is less than this, the physical properties of the resin will deteriorate and the strength of the coating will be too weak to use it as a binder.Also, it is preferable that the average degree of polymerization of this resin is 100 to 800. If it is less than 100, the coating film of the magnetic layer will not be able to be used. The strength and thermal stability are poor, and when it exceeds 800, the dispersibility of magnetic powder and the solubility of resin decrease.

The phosphoric acid monoester used in the present invention has the general formula % formula % () (in formulas (a'), (El) and (c), R has 1 carbon number
-22 alkyl group, phenyl group, alkylphenyl group, naphthyl group, alkylnaphthyl group or alkenyl group, A is an alkylene group having 2 to 4 carbon atoms, and n is 1
~30 integer. Part or all of the hydrogen in R and A may be substituted with a halogen element, etc.
) At least one phosphoric acid monoester selected from the group consisting of:

The phosphoric acid ester compound represented by the above general formula (A) is a phosphoric acid monoester formed from phosphoric acid and an alkanol having 1 to 22 carbon atoms, (alkyl)phenol or artenol, and specific examples thereof include are monobutyl phosphate, monooctyl phosphate, monohexyl phosphate, monooleyl phosphate,
Examples include monobutyl phosphate, mononolylphenyl phosphate, and monoperfluorooctyl phosphate.

The compound represented by the above general formula (0) of the present invention is a phosphoric acid monoester derived from phosphoric acid and a lower alkylene oxide adduct of an alkanol having 1 to 22 carbon atoms, (alkyl)phenol or artenol. A specific example is monododecyl polyoxyethylene (3
) phosphate, monododecyl polyoxyethylene (9
) phosphate, monoperfluorobutylpolyoxyethylene (5) phosphate, monoethylpolyperfluorooxypropylene (6) phosphate, monododecylpolyoxypropylene (9) phosphate, monooctylpolyoxypropylene (6) phosphate Phate, monooctadecenylpolyoxypropylene (8) phosphate, mononolylphenylpolyoxyethylene (
4) phosphate, monobutylphenyl polyoxyethylene (6) phosphate, monooleyl polyoxyethylene (4) phosphate, etc.

Further, the compound represented by the general formula (c) is a phosphoric acid monoester derived from phosphoric acid and a lower alkylene oxide of a fatty acid having 1 to 22 carbon atoms, and specific examples thereof include C+ t II z 5cOo (C1l zclI
to) t. PO(Oll) zCI? II. C0G(
CIlIC1l! 0) 3PO (011) Word Cttl1
3sCOO(ChCFtO) I 5Po(Oll)
tCsF+ +COO(ChCF(CPs)0) t
PO(011) tCllz:C(C1h)C00(C
IIzCHzO)PO(011)zCllt:C(C
11s) COOC1hCII (Clh CJ!) OP
O(OR) etc.

Phosphoric acid monoester is usually commercially available as a mixture with phosphoric diester under the common name of acidic phosphoric ester, but even such a mixture can of course be used in the present invention as long as it contains a monoester. It is possible.

The reaction between the vinyl chloride resin having an epoxy group and the phosphoric acid monoester compound can be carried out under mild conditions at 0° C. to 80° C. in a solvent that dissolves both. Of course, it is also possible to proceed in a molten state using a mixing roll, Banbury mixer, etc.
It is difficult to control the parallel crosslinking reaction, and the amount of the phosphoric acid monoester compound is equal to or less than the epoxy group in the vinyl chloride resin based on 100 parts by weight of the vinyl chloride resin.
If the amount used exceeds 0 equimole, which is used in the range of 0.1 to 4.0% by weight of POa, the amount of unreacted phosphoric acid monoester compound will be large and the durability of the magnetic recording medium will decrease. Not only that, but the effect of the present invention, which is that the reaction product can be used as it is to create magnetic paint without purification, cannot be expected, and 0.1% by weight as PO4
If it is less than 4% by weight, the magnetic powder dispersibility will not be exhibited, and if it exceeds 4% by weight, the generation of parallel crosslinking reactions cannot be suppressed.
To suppress the crosslinking reaction, add 1/3 of the epoxy group in the resin.
~1750 moles of phosphoric acid monoester are reacted at as low a temperature as possible, and after the reaction, excess epoxy groups are reduced by adding a monobasic acid such as hydrochloric acid to form the epoxy group in the target vinyl chloride resin. The basic ■ is 0.5!
I! It is effective to suppress it to below ffi%. However, -
The total amount of the basic acid used together with the phosphoric acid monoester needs to be less than equimolar to the epoxy group in the resin.

Another effective method for suppressing crosslinking is to add a small amount of water to the reaction system. The added water can be easily removed after the reaction by a method such as azeotropy.

The reaction product thus obtained has a phosphoric acid group in the form of phosphoric diester, and upon cleavage of the epoxy group -X-0
It has 11 hydroxyl groups.

The amount of hydroxyl groups based on -X-011 groups bonded to the resin is 0
, 1 to 2.0% by weight is preferred; if it is less than 0.1% by weight, the crosslinking effect of the coating film by the isocyanate compound will not be exhibited, and if it is more than 2.0% by weight, the pot life of the paint will be too short. When used, the amount of hydroxyl groups is much smaller than that of vinyl chloride-vinyl alcohol-vinyl acetate copolymer, which has been known for use in magnetic carbonaceous materials. The crosslinking reaction with the compound is fully achieved. The reason for this is not clear, but it is thought to be due to the fact that the hydroxyl groups that participate in the reaction are farther away from the main chain of the copolymer, increasing the degree of freedom, and that the distribution of the hydroxyl groups in the polymer is more uniform. .

The resin obtained by the present invention is generally a flexible material such as a polyurethane resin, a polyester resin, an acrylonitrile-butadiene copolymer, or a polyisocyanate resin, as well as a general vinyl chloride resin binder for magnetic paints. It is prepared and used as a solution in any solvent together with a crosslinking agent and magnetic powder, and further, if necessary, known materials such as a lubricant, a dispersant, an antistatic agent, and an abrasive.

In addition, since the resin obtained by the present invention has hydroxyl groups that are not dependent on vinyl alcohol, there is no deterioration of the resin due to saponification treatment, and the resin obtained by the present invention does not deteriorate due to the previously known vinyl chloride-vinyl alcohol-vinyl acetate combination. Compared to polymers and conventional phosphate group-containing vinyl chloride copolymers that use them as starting materials, they can exhibit superior heat resistance stability, so they are highly reliable and do not cause head corrosion. This makes it possible to manufacture magnetic recording media that are difficult to manufacture.

In addition, as desired, together with the resin obtained by the present invention,
Common resin binders for magnetic coatings such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl alcohol-vinyl acetate copolymer resin, cellulose resin, phenoxy resin, amino resin, epoxy resin, butyral resin, and acrylic resin. It is also possible to use them together.

Further, as the magnetic powder, metal magnetic powders such as Fe powder and Co powder are more preferably used, but T-Fezes
, Fe30a, Co-containing r -Fe2O2, Co-containing F
Iron oxide powders such as e5Oa, barium ferrite, and Cry powders are also used.

(Effect of the invention) The phosphoric acid monoester compound used in the present invention is originally used as a dispersant for magnetic paint, and as long as it is used within the scope of the present invention, the unreacted phosphoric acid monoester compound According to the method of the present invention, phosphoric acid groups and -X-01 can be removed even if they remain.Thus, according to the method of the present invention, phosphoric acid groups and -X-01
It is possible to produce a vinyl chloride-based magnetic paint having both 11 and 11.

(Example) The present invention will be described in more detail with reference to Examples below. In addition, parts and percentages in Examples and Comparative Examples are based on weight unless otherwise specified.Also, the amount of phosphoric acid and the amount of hydroxyl groups in the modified product are based on the amount of phosphoric acid and hydroxyl group after the modified product was purified with a tetrahydrofuran-methanol system. , determined by nuclear magnetic resonance analysis and infrared absorption analysis.

Example 1 A vinyl chloride resin (a) obtained by copolymerizing vinyl chloride, allyl glycidyl ether, and vinyl acetate, with an average degree of polymerization of 400, an epoxy content of 2.0%, and a vinyl acetate content of 2.0%.
) in 300 parts of methyl ethyl ketone, 1.2 parts of motubutyl acid phosphate (a mixture of 83% monobutyl phosphate and 17% dibutyl phosphate) (0.14 times the mole of epoxy) and 1 part of water. After stirring and mixing at 60° C. for 6 hours, 4 parts of 35% hydrochloric acid was added, the temperature was raised, and about 100 parts of methyl ethyl ketone were distilled off together with water to obtain 300 parts of a solution of resin (^).

The bound phosphoric acid of (A) is 0.42% as PO,11,
The content of hydroxyl groups was 0.70%.

Example 2 A chlorinated vinyl chloride resin with a chlorine content of 68%, obtained by post-chlorinating polyvinyl chloride with an average degree of polymerization of 380, was
After dehydrochlorination treatment in a nitrogen stream at 0° C., the resin was epoxidized with perbenzoic acid in benzene to obtain a chlorinated vinyl chloride resin (b) having an epoxy group content of 3%. This resin 1
00 parts was dissolved in 400 parts of methyl ethyl ketone, 0.6 parts of monophenyl phosphate (0.05 times the mole of epoxy) was added, and the mixture was stirred at 40°C for 244 hours.
8 parts of 5% hydrochloric acid was added, the temperature was raised, and methyl ethyl ketone was distilled off together with water to obtain 350 parts of a dehydrated resin (B) solution.

The bound phosphoric acid in (B) was 0.2% as PO411, and the hydroxyl group was 1.1%.

Example 3 The same procedure as in Example 1 was carried out except that monoperfluorobutyl phosphate (0.16 times the mole of epoxy) was used as the phosphoric acid monoester instead of monobutyl acynod + phosphate. , a resin (C) solution was obtained. (C
), the bound phosphoric acid was 0.25% as PO,H, and the hydroxyl group was 0.6%.

Comparative Example 1 Commercially available vinyl chloride-vinyl acetate-vinyl alcohol copolymer (&tl composition: 91% by weight of vinyl chloride, 3% by weight of vinyl acetate)
% by weight, 100 parts of vinyl alcohol (6% by weight), 10 parts of disodium monochloromethyl phosphate, and 500 parts of dimethylformamide were stirred and mixed at 20°C, and 5 parts of pyridine was dropped little by little into this mixture. Continue stirring and mixing for an hour.

The temperature of the resulting reaction solution was raised, and dimethylformamide was distilled off under reduced pressure to obtain 400 parts of resin (D) solution (300 parts).
(D
), the bound phosphoric acid content was 0.2%, and the amount of 011 was 1.9%.

Comparative Example 2 A resin (H) solution was obtained in the same manner as in Example 1, except that 10 parts of motuputyl acid phosphate (1.16 times the mole of epoxy) was used. The bound phosphoric acid in (E) was 1.2% as PO,11, and the hydroxyl group was 0.7%.

(Preparation and evaluation of magnetic paint) A magnetic paint was prepared using the modified products obtained in Examples 1 to 3 and Comparative Example 1.2 and a commercially available vinyl chloride resin according to the following procedure.

First, high-speed shear dispersion was performed for 90 minutes using the composition shown below.

Cobalt magnetized iron oxide 100 (specific surface area 44rrr/g) Vinyl chloride resin 10 Carbon black 5 Alumina 3 Stearic acid 0.5 Silicone oil 1.0 Methyl ethyl ketone
45 Cyclohexanone 45 Toluene
45 When the vinyl chloride resin was used as a solution, methyl ethyl ketone was added in an amount equivalent to the solvent, and the amount of the solvent was kept constant.

A mixed solution having the following composition was added to the obtained mixed solution, and the mixture was further mixed and dispersed for 30 minutes.

Vinyl chloride resin 2 Polyurethane resin 8 (Niflan N-2304 manufactured by Nippon Polyurethane Industries Co., Ltd.) Polyisocyanate
2 (Japan Polyurethane Kogyo Co., Ltd.) L) Methyl ethyl ketone 35 Cyclohexanone 35 Toluene
35 The thus obtained magnetic paint was coated on a polyester film with a thickness of 20 μm to a dry thickness of 5 μm using a blend coater, the gloss of the coated surface was measured after drying by magnetic field orientation, and the glossiness of the coated surface was measured after drying. After crosslinking for 48 hours in an atmosphere of 60° C. and 50% relative humidity, the tape was cut into 12 and 65 as wide pieces to prepare magnetic tape test pieces, which were subjected to the following tests.

(1) The reflectance at a 60° reflection angle of the coating film before glossy surface formation treatment was measured using a gloss meter.

(2) A part of the crosslinkable sample was taken and rubbed with absorbent cotton impregnated with methyl ethyl ketone, and the degree of removal of the coating film was expressed in the following three grades.

○: Film fell off or almost none △: Slightly fell off ×: A lot of film fell off (3) Orientation (Br/8m) The sample was cut into 50 nm lengths and measured using a magnetic property measuring device.

(4) Durability A sample with a length of 50 cm was placed in contact with a rotating drum covered with abrasive paper under a load of 100 g in an atmosphere of 40°C and 80% relative humidity, and rotated at 150 rpm to adhere to the abrasive paper. The degree of contamination was visually observed and indicated in the following three levels.

○: No stains △: Some stains ×: Severe stains (5) A sample was brought into contact with a rotating aluminum drum with a corrosive mirror finish, and left in an atmosphere of 65°C and relative humidity of 90% for one week. The corrosion status of the sample contact surface was visually observed and displayed in the following three stages.

O: No change Δ: Some dirt x: Jl; Eating too much The results are shown in the table.

As is clear from the table, according to the method of the present invention, magnetic powder can be dispersed well without purification after the reaction, and it is also highly durable, with no decrease in characteristics even after long-term use. A magnetic recording medium free from such concerns can be obtained.

Claims (1)

[Claims] Phosphoric acid group and - characterized by reacting a phosphoric acid monoester compound with a vinyl chloride resin having an epoxy group.
A method for producing a resin for magnetic paint having an X-OH group (X is an organic residue).