JPS61145232A - Easily bondable polyester film - Google Patents

Abstract

PURPOSE:The title film excellent in solvent resistance and bondability, obtained by applying a specified hydrophilic self-crosslinking polyurethane composition to at least either of the surfaces of a polyester film and curing this by heating. CONSTITUTION:A hydrophilic self-crosslinking polyurethane composition is obtained by reacting a polyol of a MW of 200-20,000, containing a compound having at least three hydroxyl groups in the molecule with a polyisocyanate compound at 60 deg.C or below for 5min-1hr. An aqueous coating solution obtained by dissolving 30wt.% this composition in water is applied to at least either of the surfaces of a non-oriented polyester film at a coating weight of 0.5-20 g/m<2>, dried, stretched and heat-treated to effect curing of the polyurethane composition and the crystallization of the polyester by orientation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an easily adhesive polyester film, and more particularly to an easily adhesive polyester film having brimer darkness with excellent solvent resistance and adhesive properties.

BACKGROUND OF THE INVENTION It is known to melt extrude and form films from thermoplastic polyesters, such as polyethylene terephthalate or copolymers thereof, polyethylene bupthalate or copolymers thereof, or blends thereof with small proportions of resin. It is also known that the resulting biaxially stretched and heat-set polyester film is superior in heat resistance, gas barrier properties, electrical properties, and chemical resistance f1 compared to films made of the above resin. However, since the surface is highly crystal oriented, the surface has high cohesion and poor receptivity to paints, adhesives, inks, etc.

Therefore, various methods have been proposed to improve the receptivity of the polyester film surface. One of them is to provide a primer layer (undercoat layer) on the polyester film surface in advance, and then form a thin surface layer that is different from the film. Methods for forming desired layers such as magnetic layers, optical recording layers, etc. are known.

Although the formation of the undercoat layer is generally carried out in a process separate from the polyester film forming process, there is a risk that dust such as dirt and foreign matter may be mixed in during this process. Advanced processed film products, such as audio magnetic tape,
Magnetic tape for video.

] Magnetic tape for computer, floppy disk, X
In applications such as line photographic film, photographic film for printing, and diazo microfilm that must maintain delicate quality, even if an easily adhesive surface is successfully formed, the resulting film may suffer from surface defects due to dust. If so, the base film cannot be used for these purposes, so the coating process must be performed in a clean place.

By the way, there is a polyester film manufacturing process where this clean bamboo can be satisfied, and if primer treatment can be performed in this process, it will be possible to fully support the use of the above-mentioned advanced film processed products. Therefore, it is desirable to perform in-line subbing processing in such a film manufacturing process.

In the conventional technology, the method of modifying the surface of a polyester film to make it easily adhesive by treating the surface with a primer is often the method of modifying the surface of a polyester film to make it an easily adhesive surface.
This has been achieved by applying one substance to the surface layer of the film. If such a method is carried out during film production,
Contamination of the surrounding environment due to fugitive organic solvents, safety and hygiene -
The use of organic solvents should be kept to a minimum as much as possible, since this may lead to unfavorable conditions and adversely affect the T culm produced. Therefore, when performing in-line subbing treatment in the film forming process, it is preferable to use a composition using water as a solvent from the viewpoints of process, economy, and safety.

Many primer compositions using water as a solvent have been known, and many proposals have been made for, for example, aqueous solutions or dispersions of polyurethane. however,
These coatings have poor solvent resistance and, as mentioned above, are not preferred.

For example, coatings made of non-reactive polyurethane emulsions have a problem of low solvent resistance. If the solvent resistance of the film formed under the polyester film is low, for example, when a magnetic layer is applied on a single layer of primer (film), the first layer of primer and the magnetic layer will mix, causing turbulence in the flow on the coated surface. Flow lines occur in the magnetic layer, and a good magnetic surface is obtained. In particular, in recent years, magnetic layers have become thinner in order to cope with higher magnetic densities, and in particular, in floppy disks, the thickness has been reduced to about 1 μm. The flow of sushi becomes clearer.

For the above-mentioned reasons, there is a demand for an easily adhesive film coated with a single layer of primer having high solvent resistance.

OBJECT OF THE INVENTION An object of the present invention is to provide an easily adhesive polyester film with excellent solvent resistance. Other objects of the invention are various coatings applied to polyester films, such as cellophane inks, magnetic paints, gelatin compositions, offset inks, N-child photographic toners, chemical matte paints, diazo paints.

A specific primer layer that has excellent adhesion to heat-sealable compositions, inorganic film-forming substances, etc., and has excellent diarrhea resistance and does not cause runny when applying a yeast coating layer. An object of the present invention is to provide an easily adhesive polyester film formed by coating.

Another object of the present invention is to provide a polyester film with excellent solvent resistance that is made easily adhesive by in-line subbing treatment.

Structure of the Invention According to the present invention, the object of the present invention is to: 1. apply an aqueous coating solution containing a hydrophilic self-crosslinking polyurethane composition having intramolecularly blocked isocyanate groups to at least one surface of a polyester film; An easily adhesive polyester film obtained by heating and curing.

2. An aqueous coating solution containing a hydrophilic self-crosslinking polyurethane composition having intramolecularly blocked polyisocyanate groups is applied to at least one surface of the polyester film before crystal orientation is completed, and then dried, stretched, and further An easily adhesive polyester film obtained by heat treatment to complete oriented crystallization.

achieved by

In the present invention, polyester is a linear saturated polyester synthesized from an aromatic dibasic acid or its ester-forming derivative and a diol or its ester-forming derivative. Examples include polyethylene terephthalate, polyethylene isophthalate 1-, polybutylene terephthalate, polyethylene-2,6-naphthalene dicarboxylate, and copolymers of these or blends of these with a small proportion of loose resin. included. The polyester film of the present invention is obtained by melt-extruding the above linear saturated polyester resin, forming it into a film by a conventional method, and subjecting it to oriented crystallization and heat treatment crystallization.

The crystals of this polyester film are oriented to such an extent that the heat of crystal fusion measured by a scanning calorimeter in a nitrogen stream at a reservoir speed of 10°C/min is usually 4 cal/y or more.

In the present invention, a polyester film before completion of crystal orientation refers to an unstretched film obtained by thermally melting the polymer and forming it into a film as it is; an unstretched film oriented in either the vertical direction or the horizontal direction. A uniaxially stretched film; furthermore, it is stretched at a low magnification in two directions, the vertical direction and the horizontal direction, and then finally re-stretched in either the vertical direction or the horizontal direction to complete the oriented crystallization. (stretched film), etc.

The aqueous coating liquid applied to the film in the present invention is an aqueous coating liquid containing a hydrophilic self-crosslinking polyurethane composition having blocked isocyanate groups in its molecules.

Blocking agents that block the free isocyanate groups of the polyurethane include bisulfites.

Phenolic compounds, alcohols, oximes.

Active methylene compounds, lactams, mercaptan compounds,
Examples include imine compounds, amide compounds, imidazoles, imide compounds, etc., but especially bisulfite Fi! such as sodium bisulfite and potassium bisulfite! Preferably, salt is used. Bisulfite has a low temperature (11) and can shorten the heat treatment time, and is also water-soluble, and when it is additionally bonded to polyurethane molecules as a blocking agent, it imparts anionic and ionic hydrophilic properties to polyurethane. This is convenient because it is possible to Preferred metals for the salt are alkali metals, particularly sodium.

Before blocking free isocyanate groups, the polyurethane is prepared by reacting the polyol with an excess amount of a polyfunctional isocyanate compound and, if necessary, a chain extender having an active hydrogen atom, until the reaction product is substantially free of gel components. You can get it by doing this. In this case, it is preferable to include a compound having three or more hydroxyl groups in the molecule as the polyol.

Examples of the polyfunctional isocyanate compounds include aliphatic diisocyanates such as 1,4-butane diisocyanate, 1,6-hexane diisocyanate, 2,2,4- and '2,4,4-trimethylhexamethylene diisocyanate, boron diisocyanate, 4.
Alicyclic diisocyanates such as 4'-dicyclohexylmethane diisocyanate and cyclohexane diisocyanate, isomers of toluylene diisocyanate,
4. Aromatic diisocyanates such as 4'-diphenylmethane diisocyanate, araliphatic diisocyanates such as xylylene diisocyanate, and polyisocyanates prepared by adducting these with polyhydric alcohols, glycols, or polyamines, and containing epoxy groups. Examples include polyisocyanates. These can be used alone or as a mixture of two or more.

In addition, the above polyols include ethylene glycol,
diethylene glycol, dipropylene glycol, 1,
Glycols such as 4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexane dimetatool, etc., polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol, etc.
Examples include polyether glycols such as polyethylene glycol, polytrimethylene glycol, polytetramethylene glycol, etc., polyesters and polyether esters having two or more hydroxyl groups, polynityls having two or more hydroxyl groups, etc. can. Among these, those having two or more hydroxyl groups and having a molecular weight of 200 to 2
0,000 polyols are preferred, and these are preferably used in combination with polyhydric alcohols.

The above polyesters and polyether esters include polyvalent saturated and unsaturated carboxylic acids such as succinic acid, adipic acid, phthalic acid, maleic anhydride, or their acid anhydrides, and ethylene glycol, diethyl glycol]- 1,4-butanediol, neopentyl glycol,
From polyvalent saturated and unsaturated alcohols such as 1,6-hexanediol, trimethylolpropane, etc., relatively low molecular weight polyether glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc., and mixtures thereof. There are mainly linear or branched condensation products obtained, and rough 1
It is also possible to use polyesters made from polyesters and hydroxy acids, as well as polyetheresters prepared by adding ethylene oxide, propylene oxide, etc. to previously produced polyesters.
Also, examples of the chain extender include cyamic acid such as ethylenediamine, hexamethylenediamine, piperazine, the above-mentioned low molecular weight glycols and polyhydric alcohols, and water.

When producing polyurethane from these, it is preferable that the polyurethane (oligomer) contains about 10 to 40% by weight of oxyalkylene chains, particularly oxyethylene chains. In addition, the molar ratio of isocyanate group/active hydrogen atom can be freely selected from 1 or more, but the i
*0 It is desirable that the isocyanate group content be 10% by weight or less, preferably 7% by weight or less. The blocking ratio of free isocyanate can be determined by a conventionally well known method. When bisulfite is used as a blocking agent, the process can be carried out by mixing and stirring at a low temperature of 60° C. or lower for 5 minutes to 1 hour.

In this way, a hydrophilic self-crosslinking polyurethane composition having blocked isocyanate groups in the molecule is obtained. A representative example of this product is Elastron, a trade name manufactured by Daiichi Kogyo Seiyaku ■. Elastron has isocyanate groups blocked with sodium sulfite, and has a carbamoyl sulfonate group at the end of the molecule, which has strong hydrophilic properties, making it water-soluble. The blocking agent is dissociated by a certain heat treatment, and the regenerated active isocyanate groups cause a self-crosslinking reaction between molecules, ultimately producing a polyurethane film with a three-dimensional wire structure.

The hydrophilic self-crosslinking polyurethane composition can be adjusted to an appropriate concentration with water to form an aqueous coating solution. In the present invention, the step of applying the aqueous coating liquid may be a normal coating step, that is, a step of applying the biaxially stretched and heat-set polyester film, but it is preferably performed during the polyester film manufacturing process. In particular, it is preferable to apply it to a polyester film before crystal orientation is completed. The solid content concentration of the aqueous solution is usually 30% by weight or less, preferably 10% by weight or less.

These water-based coating solutions have a coating rate of 0 per film running.
．． An amount of 5 to 209 g, preferably 2 to 10 g, is applied to ensure adhesion. The film coated with the aqueous coating solution is guided to a tenter for stretching and heat setting, where it is heated to volatilize water and cause a polyurethane crosslinking reaction to form a stable film, forming an easily adhesive polyester film. shall be.

A catalyst may be added to the aqueous coating solution of the present invention in order to promote the thermal crosslinking reaction. Inorganic substances as catalysts,
Salts, organic substances, alkaline substances.

Various substances such as acidic substances and metal-containing organic compounds are used. Furthermore, an alkaline substance or an acidic substance may be added to adjust the pH of the aqueous solution.

When applying an aqueous coating liquid to the surface of a polyester film, a required amount of a surfactant such as an anionic surfactant or a nonionic surfactant may be added.

As an effective surfactant, the surface tension of the coating liquid is 40d.
yne/cm or less and promotes leakage into polyester films, such as polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, fatty acid metal soap, Alkyl sulfate.

Examples include alkyl sulfonates, alkyl sulfosuccinates, quaternary ammonium chlorides, and alkylamine hydrochlorides.

The polyurethane composition of the present invention contains an antistatic agent as long as it does not lose its contributing effect.

There is no problem in mixing various additives such as ultraviolet absorbers, plasticizers, pigments, organic fillers, inorganic fillers, and lubricants.

Any known coating method can be used to apply the aqueous polyurethane solution of the present invention. For example, roll coating method,
[gravure]-to method, roll plush method, spray coating, air knife coating.

It is preferable to apply an impregnation method, a curtain coating method, etc. alone or in combination.

Effects of the Invention The easily adhesive polynisdel film of the present invention exhibits extremely good adhesion to cellophane inks, 11-ki coatings, geladine compositions, electrophotographic toner compositions, chemical matte coatings, etc. , methyl ethyl ketone, toluene,
Shows high solvent resistance to magnetic paint solvents such as edyl acetate, bubbly acetate, ethanol, dioxane, tetrahydrofuran, cyclohexane, and cyclohexanone.

EXAMPLES The following examples will be explained below. Note that parts in the examples mean parts by weight. Moreover, each characteristic of the film was measured by the following method.

1. Apply the evaluation paint prepared in the following manner to adhesive primer-coated polyester film, dry at 80°C for 1 minute, and further age at 60°C for 24 hours, resulting in an average coating thickness of 2 μm.
Roll coat so that it looks like this. This coated film is R
Head load 50g using CA wear tester (RCA company)
The adhesion is measured by the number of times the adhesive is rubbed until holes form on the coated surface.

[Preparation of paint for evaluation] Nitrocellulose R81/2 as lacquer thinner for paint
[Freus manufactured by Daicel ■ containing 25% isopropanol] was dissolved to prepare a 40 wt% solution, and the solution was
3.9 parts followed by polyester resin (Desmofene #1
700 manufactured by Bayer > 32.5 parts, chromium dioxide magnetic powder 2.60 parts 1 Soybean oil fatty acid resin A P as a dispersant/wetting agent: Riken Vitamin (IIWIJ), cationic activator (cation A8 NOF ( II) and Screen (shark liver oil) at 1 part, 0.5 part, and 0.8 part, respectively.
part into a ball mill. Methyl ethyl ketone (MF
K and abbreviated below) / cyclohexanone / toluene - 3/4
282 parts of a mixed solution consisting of /3 (weight ratio) is further mixed and sufficiently pulverized to prepare a mother liquor paint (45 wt%). To 50 parts of this mother liquor, 48 parts of an addition reaction product of trimethylolpropane and toluleine diisocyanate
A magnetic paint for evaluation containing 6.25 wt % butylacetate (Coronate I-: manufactured by Nippon Polyurethane Industries) was obtained.

2. Apply a drop of tetrahydrofuran (approximately 0.02 cc) to the surface of the polyester film coated with a solvent-resistant primer using a dropper.
Drop it, place gauze on top of it, place a 100g weight on it, and move the gauze at a speed of about 10QQmmZ.

After drying, samples not treated with tetrahydrofuran and those treated with tetrahydrofuran were examined using interference micrographs at a magnification of 400 times, and the changes in the surface of the primer were evaluated as follows.

・Those where the primer has almost disappeared: ×・Those with almost no change: ○ ・Those with slight changes depending on the degree of change in surface morphology between the two: ○~Δ ・Those that have changed considerably: ×~△ ・No change Intermediate: Mark as △.

Example 1 Heavy fiIIIlFl! 20% aqueous solution of self-crosslinking polyurethane having isocyanate groups blocked with t-soda [manufactured by Daiichi Kogyo Seiyaku (41: trade name: Elastron C-9)]
] 80 parts (as solid content) and 20 parts (as solid content) of polyoxyethylene nonyl ether [+-I L B = 17.8: manufactured by NOF ■, trade name N5240] were thoroughly mixed. Use a coating liquid with a solid content concentration of 1%.

This coating solution was applied to a biaxially stretched and heat-set polyethylene terephthalate film with a thickness of 75 μm using the kiss coat method, and then heat-treated in a drying zone at 140°C for 45 seconds to form a primer-coated polyester film with an average coating M' of 150 m9/rd. Obtained.

The properties of this film are shown in Table 1.

Example 2 A 20% aqueous solution of self-crosslinking polyurethane having isocyanate groups blocked with sodium bisulfite [Daiichi Kogyo Seiyaku @ Kosei: trade name Elastron C-9 185 parts (as solid content) and polyoxyethylene nonylphenyl ether [ 1-ILB, 17,8. Nippon Oil & Fats (1 Wooden Co., Ltd., trade name N5240, 115 parts solids) was thoroughly stirred and mixed to obtain a coating solution with a total solids concentration of 3%.

Specificity measured in 0-chlorophenol at 25°C
Polyethylene terephthalate (containing lubricant) with a viscosity of 0.65 was melt-extruded onto a rotating drum maintained at about 20°C to obtain an unstretched film of 950 μm, which was then stretched 3.5 times in the machine axis direction. The above coating liquid was applied to both sides of a uniaxially stretched film by a kiss coating method. Part 49
It passed through a preheating zone at 100°C and was laterally stretched 3.6 times at 105°C, followed by heat treatment at 210°C for 5.5 seconds, with an average coating Ji of 30 mg/TIt and a thickness of 75 m.
A double-sided primer-coated biaxially oriented polyester film of m was obtained. The properties of the film are shown in Table 1.

Comparative Example 1 85 parts of a 25% aqueous solution of non-reactive aqueous polyurethane [Hytran W140 manufactured by Dainippon Ink Co., Ltd.] and polyoxyethylene nonylphenyl ether [1-11-8=
12.9 + Manufactured by NOF: Product name N 82085]
15 parts (as solid content) were sufficiently stirred and mixed to obtain a coating liquid with a total solid content concentration of 3%.

This liquid was applied to a biaxially oriented polyester film in the same manner as in Example 2 to obtain a biaxially oriented polyester film coated with primer on both sides. Its properties are shown in Table 1.

Although this film has high adhesion, it has low solvent resistance, and smearing occurred on the coated surface during thin magnetic coating.

Comparative Example 1 The same procedure as Example 2 was carried out except that the primer treatment was not performed. The properties of the obtained film are shown in Table 1.

(Margin below)

Claims (1)

[Scope of Claims] 1. By applying an aqueous coating solution containing a hydrophilic self-crosslinking polyurethane composition having a blocked isocyanate group in its molecules to at least one surface of a polyester film and curing it by heating. The obtained easily adhesive polyester film. 2. The free isocyanate groups of the polyurethane composition obtained by the reaction of a polyol containing a compound having three or more hydroxyl groups in the molecule with a polyfunctional isocyanate compound are blocked with a hydrophilic blocking agent. The easily adhesive polyester film according to claim 1, which is a polyester film. 3. Applying an aqueous coating solution containing a hydrophilic self-crosslinking polyurethane composition having intramolecularly blocked isocyanate groups to at least one surface of the polyester film before crystal orientation is completed, followed by drying, stretching, and heat treatment. An easily adhesive polyester film obtained by completing oriented crystallization. 4. The above polyurethane composition is obtained by reacting a polyol containing a compound having three or more hydroxyl groups in the molecule with a polyfunctional isocyanate compound, and the free isocyanate groups of the polyurethane composition are blocked with a hydrophilic blocking agent. The easily adhesive polyester film according to claim 3, which is a polyester film.