JPH0680121B2 - Primer coating agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a primer coating agent, particularly a primer coating agent for polyester, and more specifically, it is characterized by containing a specific aqueous polyester polyurethane resin, The present invention relates to a primer coating agent which is excellent in adhesion to various adherends coated on a polyester layer and a primer layer obtained by the treatment agent of the present invention, and is also excellent in blocking resistance and water resistance.

<Prior Art> A biaxially stretched polyester film, especially a polyethylene terephthalate film (hereinafter abbreviated as PET film) is superior in electrical insulation, transparency, dimensional stability, and toughness. It is used in a wide range of fields such as insulating materials, drawing, photographic film, magnetic tape, metal evaporated film, and various packaging materials.

However, since the surface of PET film is generally highly oriented, the activity of the surface is poor, and the PET film is coated with printing ink, magnetic paint, metal deposition layer, various photosensitive materials, adhesives, etc. It has the drawback of poor adhesion. Therefore, the PET film surface is usually activated by various methods in order to improve the adhesiveness with other substrates, and one method is primer coating.

Conventionally, an aqueous polyurethane resin or an aqueous polyester resin has been mainly studied as an aqueous processing agent for primer coating. For example, an easily adhesive polyester film (application of water-based polyurethane resin, Japanese Patent Publication No. 57-2623)
No. 6), a method for producing an easily-adhesive polyester film (coating of an aqueous polyester resin containing a sulfonate group in the molecule, JP-A-58-1727), a water-soluble polyester adhesive (containing a sulfonate group And an aqueous polyester resin containing a phosphorus compound, Japanese Patent Publication No. 56-5476).

<Problems to be Solved by the Invention> However, although the above-mentioned aqueous polyurethane resins represented by Impranil DLH and DLN have good adhesiveness to various adherends, generally, an aliphatic polyester polyol or polyether polyol is used. Since it is the main component, the adhesion to the PET film is basically not sufficient, and therefore, it is necessary to apply a stretching treatment after coating the polyester film before the crystal orientation is completed. At present, however, sufficient adhesiveness has not yet been obtained.

Further, since such a polyurethane resin forms a flexible film rich in elasticity, it has a drawback that blocking is likely to occur. On the other hand, the above aqueous polyester resin is PET
Adhesion to the film is good, but both contain a large amount of sulfonic acid metal base as a hydrophilic group in order to obtain sufficient water dispersibility. Therefore, even after drying, it remains as a hydrophilic group in the film and has sufficient water resistance. Properties cannot be obtained, and the adhesiveness and film properties that can withstand practical use cannot be maintained under high humidity or in a water-immersed state, and blocking tends to occur over time due to moisture absorption, for example, a PET film treated with a primer is rolled up. In that case, there is a problem that the handling becomes very difficult due to the sticking of the film surface, and not only the workability is greatly reduced, but also the commercial value is reduced.

<Means for Solving Problems> From such a viewpoint, the inventors of the present invention, regarding the primer coating agent for a polyester film, are particularly excellent in adhesiveness with PET film, durability such as water resistance and solvent resistance, and excellent in blocking resistance, The present invention has been achieved as a result of earnest research on a primer coating agent having excellent adhesion to various adherends coated on the primer layer.

That is, the present invention comprises an acid component (A-1) consisting of (A) aromatic dicarboxylic acid / fatty (ring) dicarboxylic acid = 70/30 to 100/0 (weight ratio) and a glycol component (A-2). A polyester polyol, a (B) polyisocyanate compound, and (C) a chain extender, if necessary, which contains 0.5 to 6% by weight of pendant carboxyl groups. The present invention provides a primer coating agent containing an aqueous polyester polyurethane resin in which the carboxyl group is neutralized with ammonia or an organic amine.

The present invention is applicable to, for example, plastic, metal (aluminum, iron,
It can be used as a primer coat for copper, glass, paper, wood, etc., but is particularly suitable for plastics. Examples of the plastic include vinyl chloride resin, polyamide resin (nylon), polyester resin, unsaturated polyester resin, polyurethane resin, acrylic resin, ethylene / vinyl acetate copolymer, ethylene / vinyl alcohol copolymer, and the like. Among them, polyester resin is particularly preferable. Examples of the polyester resin in the present invention include polyalkylene terephthalate as a main component, for example, films, sheets and molded products such as polyethylene terephthalate and polybutylene terephthalate, and other aromatic dicarboxylic acids such as isophthalic acid. Also included are films, sheets, molded products, etc. of copolymers of 2,6-naphthalenedicarboxylic acid and the like, or mixtures thereof.

Further, the present invention is an effective primer coating agent for a polyester resin without surface treatment,
In order to further enhance the effect of the primer coating, the primer coating agent of the present invention can be used for a polyester resin which has been physically or chemically treated in advance by corona treatment, plasma treatment, alkali treatment or the like.

Polyester polyol used in the production of the aqueous polyester polyurethane resin of the present invention, the high molecular weight obtained by the excellent adhesion to PET film, as well as excellent water resistance, in order to impart blocking resistance, its acid It is essential and essential that the component (A-1) is mainly an aromatic polyester polyol composed of aromatic dicarboxylic acid / fatty (ring) dicarboxylic acid = 70/30 to 100/0 (weight ratio). When the amount of aromatic dicarboxylic acid in A-1) is less than 70% by weight, the flexibility of the film and the resistance to impact peeling are improved, but especially the adhesion to PET film and the water resistance and blocking resistance of the film. Is markedly reduced, which is inappropriate.

Examples of the aromatic dicarboxylic acid as the acid component (A-1) used in the present invention include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid and 2,6- Aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, and 1,2-bis (phenoxy) ethane-P, P'-dicarboxylic acid, and their anhydrides or ester-forming derivatives, p-hydroxybenzoic acid , Aromatic hydroxycarboxylic acids such as p- (2-hydroxyethoxy) benzoic acid and their ester-forming derivatives.
Further, as the aliphatic (cyclic) dicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, maleic anhydride, fumaric acid and other aliphatic dicarboxylic acids, 1,3-cyclopentanedicarboxylic acid, 1,4- Examples thereof include alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and their anhydrides or ester-forming derivatives. No carboxyl groups are supplied from these acids.

The glycol component (A-2) is a compound having two hydroxyl groups, such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6 -Hexanediol, neopentyl glycol, diethylene glycol,
Aliphatic diols such as triethylene glycol, polyethylene glycol and dipropylene glycol; alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol, bisphenol A, hydroquinone and their alkylene oxide adducts Examples include diols. The polyester polyol of the present invention has the following formula: aromatic dicarboxylic acid / fatty (ring) dicarboxylic acid =
It is not limited to the copolyester polyol consisting of 70/30 to 100/0 (weight ratio), and may be a mixture of the aromatic polyester polyol and the aliphatic (cyclic) polyester polyol in the above weight ratio. .

Further, it is preferable that the aromatic polyester polyol is contained as a polyester segment in an amount of 60% by weight or more based on the solid content of the finally obtained aqueous polyester polyurethane resin.

The polyester polyol (A) used in the present invention is usually preferably a linear polymer, but the use of a polyfunctional component is not hindered as long as it does not impair the water dispersibility and adhesiveness of the obtained aqueous polyester polyurethane resin. . Examples of such polyfunctional components include polycarboxylic acids such as trimellitic acid, pyromellitic acid, and cyclohexanetricarboxylic acid, and their anhydrides or ester-forming derivatives;
Examples thereof include polyols such as glycerin, trimethylolethane, trimethylolpropane and pentaerythritol.

The average molecular weight of the polyester polyol (A) of the present invention is
It is preferably 800 to 4000, and when the molecular weight is less than 800, the content of isocyanate in the polyester polyurethane obtained from the polyester polyol becomes too large, so that the flexibility of the coating decreases and the PET becomes brittle.
Adhesion to the film is significantly reduced and the molecular weight is 40
When it exceeds 00, the solubility and the temporal stability of the obtained aqueous polyester polyurethane resin are deteriorated, which is not suitable. A more preferable molecular weight is 1000 to 3000.

Chain extender (C) optionally used in the present invention
As, pendant carboxyl group-containing diols or glycols such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, hexamethylene glycol, neopentyl glycol or ethylenediamine, propylenediamine, hexamethylenediamine, phenylenediamine, Examples include diamines such as tolylenediamine, diphenyldiamine, diaminodiphenylmethane, diaminocyclohexylmethane, piperazine and isophoronediamine, and hydrazine.

The polyisocyanate compound (B) used in the present invention includes 2,4-tolylene diisocyanate and 2,6
-Tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-
Diphenylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, lysine diisocyanate,
Isophorone diisocyanate, trimethylhexamethylene diisocyanate, 1,4-cyclohexylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4 Examples thereof include'-biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate and 1,5-tetrahydronaphthalene diisocyanate.

The method of introducing the carboxyl group for obtaining the aqueous polyester polyurethane resin having 0.5 to 5% by weight of the pendant carboxyl group of the present invention may be any conventionally known method, but preferably, for example, the general formula [Wherein R is an alkyl group having 1-3 carbon atoms]
A method using a pendant carboxyl group-containing polyester polyol obtained by copolymerizing a compound represented by (I) as a glycol component when synthesizing a polyester, or a chain extender is represented by the general formula (I). A method using a chain extender containing a pendant carboxyl group is used. Examples of the compound represented by the general formula (I) include 2,2-dimethylolpropionic acid and 2,2
Examples include dimethylol butyric acid and 2,2-dimethylol valeric acid.

As a method for introducing a pendant carboxyl group other than the above, Japanese Patent Publication No. 52-3438 (method using two carboxyl group-containing aromatic diamines as a chain extender),
JP-A-57-165420 (method using half ester from polyhydroxyl compound and dicarboxylic acid anhydride as chain extender), JP-B-53-7479 (excess polyalkylene polyamine in isocyanate-terminated prepolymer) After reacting with polyurethane urea polyamine,
Method of adding trimellitic anhydride) Japanese Patent Publication Sho 42-40677
Japanese Patent Publication (a method of synthesizing a polyester intermediate having a high acid value from a polyhydric alcohol and a polybasic acid, and reacting it with a polyisocyanate having an equivalent amount of a hydroxyl group or less).

The amount of the compound represented by the general formula (I) used is such that a stable aqueous polyester polyurethane resin is obtained,
It is an important factor for imparting excellent water resistance to the film after drying and excellent adhesion to various adherends coated on the primer layer, and the content of pendant carboxyl groups in the obtained polyester polyurethane is It is necessary to react the polyester polyurethane resin in an amount so as to fall within the range of 0.5 to 6% by weight (solid content).

When the content of the carboxyl group is less than 0.5% by weight, the water resistance of the film is remarkably improved, but the stability of the resulting aqueous polyester polyurethane resin and the adhesion to various adherends are unsuitable. On the other hand, if it exceeds 6% by weight, the adhesion to various adherends is improved, but the water resistance of the film, especially the decrease in the adhesive strength when immersed in water, is markedly inappropriate. The preferred range is 0.5 to 5% by weight.

The aqueous polyester polyurethane resin of the present invention can be produced by any conventionally known method and is preferably, for example, a carboxyl group-containing compound represented by the general formula (I) in an organic solvent which is inert to isocyanate and hydrophilic. A pendant carboxyl group-containing polyester polyol (A) obtained by copolymerizing the above is reacted with a polyisocyanate compound (B) together with a chain extender (C) if necessary, or a specific polyester polyol,
(A), the carboxyl group-containing compound of the general formula (I) and optionally a chain extender (C) are reacted with the polyisocyanate compound (B) to urethanize, and then neutralized with ammonia or an organic amine. It is produced by subjecting it to aqueous solution (desolvation under reduced pressure if necessary). In addition, during the reaction with the polyisocyanate compound (B), an equivalent amount of isocyanate groups is made excessive with respect to active hydrogen atoms to form a prepolymer less than a pendant carboxyl group-containing isocyanate, and then chain-extended in water. It can also be obtained by neutralizing and making it aqueous. However, the term "water-based" as used herein means to stably dissolve or disperse the resin in water.

Further, in order to prevent gelation in the urethanization reaction, alcohols such as methanol, ethanol and isopropyl alcohol; and reaction terminators such as glycols such as ethylene glycol and 1,3-butanediol may be used.

The molecular weight of the polyester polyurethane of the present invention thus obtained is preferably 8,000 to 100,000. It is particularly preferably 10,000 to 50,000.

Examples of the base that neutralizes the pendant carboxyl group used in the present invention include, in addition to ammonia, organic amines such as trimethylamine, triethylamine, triisopropylamine, tributylamine, triethanolamine, methyldiethanolamine, dimethylethanolamine, and diethylethanolamine. In order to improve the water resistance of the film after drying, those which are water-soluble and have high volatility that easily dissociates by heat are preferable, and ammonia, trimethylamine and triethylamine are particularly preferable.

Further, as the organic solvent which is inert and hydrophilic with respect to the isocyanate used in the present invention, for example, ethers such as tetrahydrofuran and dioxane, esters such as ethyl acetate, acetone, methyl ethyl ketone, ketones such as cyclohexanone, and dimethyl. Examples thereof include amides such as formamide and N-methylpyrrolidone, but they are usually removed by distillation under reduced pressure after hydration of the polyester polyurethane, and even when used without solvent removal, the drying speed is increased, so that water is preferable The use of lower boiling solvents is desirable.

The particle diameter of the thus obtained aqueous polyester polyurethane resin of the present invention is usually 5 μm or less, preferably 1 μm or less, more preferably 0.1 μm or less. If the particle size is large, the particles are likely to aggregate and settle out particularly when diluted, so that the transparency of the film is lowered, or the film becomes nonuniform especially when a primer coating having a film thickness of 1 μ or less is applied. Therefore, there arises a problem that the effect of the primer treatment is not sufficiently expressed.

The water-based polyester polyurethane resin of the present invention is used as it is as a primer coating agent, but in order to further improve water resistance, solvent resistance, heat resistance and other durability or blocking resistance, an amino resin and an epoxy resin are used. A crosslinking agent such as a compound, an aziridine compound and a polyisocyanate compound can be used in combination. Examples of amino resins include methylol- or alkoxymethylol-based urea resins, melamine resins, and benzoguanamine resins. Epoxy compounds include diglycidyl ethers of bisphenol A or hydrogenated bisphenol A and oligomers thereof, diglycidyl esters of terephthalic acid, succinic acid, etc., active methylene compounds of lactams of ethylene glycol, acetoacetic acid esters, sodium bisulfite, etc. The polyisocyanate compound blocked with the blocking agent and the aqueous dispersion thereof may be used.

An appropriate amount of curing agent or accelerator may be used in combination with these crosslinking agents.

The primer coating agent of the present invention further comprises, if necessary, inorganic fine particles (colloidal silica) for improving blocking or slipperiness, and anionic, nonionic hydrocarbon-based or fluorine-based interface for improving wettability. It is put to practical use by blending an activator or an auxiliary agent such as an antistatic agent.

Thus, the primer coating agent obtained by the present invention is
After being adjusted to any resin concentration, preferably 0.1 to 20% by weight, a conventionally known coating method, for example, a gravure coating method,
It is applied onto the polyester film by a rod coating method, a spray coating method, an air knife coating method, a roll coating method or the like. In order to further enhance the effect of the primer coating agent of the present invention, it may be applied during the biaxial stretching process of the polyester film, that is, before the biaxial stretching process is completed.

<Action> The primer coating agent of the present invention thus formed is coated on a PET film, dried, and optionally heat-treated, so that the surface blocking property is extremely small,
In addition, it forms a transparent and uniform film with excellent water resistance and adhesiveness, and also has excellent adhesiveness to PET film and various adherends coated on this primer layer. PE used for drawing materials, photosensitive materials, electrophotographic materials, magnetic recording materials, packaging materials, etc.
It has excellent performance as a primer coating agent for T film.

Hereinafter, the present invention will be further described with reference to Examples, but "parts" and "%" in the text are based on weight unless otherwise specified. The present invention is not limited to this.

The methods for evaluating the physical properties of the aqueous polyester polyurethane resin of the present invention are shown below.

Adhesion to PET film A biaxially stretched PET film with a thickness of 100 μm was coated with a sample aqueous dispersion so that the dry film thickness was about 2 μm.
After being dried at ℃ for 1 minute, a peeling test using a 24-mm width adhesive tape manufactured by Nichiban Co., Ltd. was carried out, and the results are shown in five grades.

1 ... Adhesive strength is very weak and peels completely.

2 ... 50% or more peeling.

3 ... 10 to 50% peeling.

4 ... Adhesive strength is fairly strong and peels off less than 10%.

5 ... Adhesive strength is very strong and never peels off.

Adhesion to magnetic coating film The above-obtained PET film after primer coating was coated with a magnetic coating composition having the following composition by a bar coater so that the film thickness when dried was about 10 μm.
After being dried at 80 ° C. and further heat-treated at 60 ° C. for 1 day, a peeling test with Nichiban adhesive tape is carried out, and the evaluation is carried out by the five grades defined in.

"Chris Bonn 4216" (Polyurethane-based urethane resin manufactured by Dainippon Ink & Chemicals, Inc.) 225 parts "Vinylite VAGH" (Salt vinyl acetate vinyl copolymer manufactured by Union Carbide Co., USA) 40 parts Cyclohexanone / methyl ethyl ketone = 1/1 (weight) Ratio) mixed solvent 435 parts γ-Fe ₂ O ₃ magnetic powder 350 parts carbon black 12 parts “Bernock D-750” (Dainippon Ink & Chemicals Co., Ltd. low molecular weight polyisocyanate) 15 parts lubricant 7 parts ink Adhesiveness to the same as above except that the following gravure ink was used instead of the magnetic paint.

"CLS-709 White" (Dainippon Ink and Chemicals, Inc. cellophane gravure ink for printing) 50 parts Mixed solvent consisting of toluene / ethyl acetate / MEK = 1/1/1 (weight ratio) 100 parts Adhesion to gelatin film A 2% aqueous gelatin solution is used in the same manner as described above except that the magnetic paint is used.

Non-blocking property PET obtained after primer coating obtained above
Laminating the films together, applying a load of 100 g / cm ² ,
After being left in an atmosphere of 40 ° C. and 65% RH for 24 hours, the film was peeled off and the tackiness at that time is shown by the following three-stage evaluation.

○: There is no tackiness at all, and it can be peeled off without making any work.

Δ: There is some tackiness, but there is no change on the coated surface.

X: A surface defect due to adhesion occurs on one of the coated surfaces.

Water resistance PET obtained after primer coating obtained above
The film is immersed in warm water at 40 ° C. for 24 hours, and then subjected to a peeling test using an Nichiban adhesive tape, and the evaluation is carried out according to a five-level evaluation.

<Preparation of Polyester Polyol> While introducing nitrogen gas in a reactor equipped with a thermometer, a nitrogen gas introducing pipe, and a stirrer, 664 parts of terephthalic acid, 631 parts of isophthalic acid, 472 parts of 1,4-butanediol, neopentyl. After 447 parts of glycol and 0.5 part of dibutyltin oxide were charged and esterified at 180 to 230 ° C. for 5 hours, polycondensation reaction was carried out at 230 ° C. for 6 hours until the acid value became <1. Then 120
After cooling to ℃, add 321 parts of adipic acid and 268 parts of dimethylolpropionic acid, raise the temperature again to 170 ℃ and react at this temperature for 20 hours to obtain a pendant carboxyl group-containing polyester polyol A having an acid value of 46.5 and a hydroxyl value of 59.8. It was Similarly, a pendant carboxyl group-containing polyester polyol F and polyester polyols B, C, D, E and G were obtained (see Table-1).

Example 1 1880 parts of polyester polyol A was dehydrated at 120 ° C. under reduced pressure and then cooled to 80 ° C., and then methyl ethyl ketone 14
12 parts were added and dissolved with sufficient stirring, then 238 parts of 4,4'-diphenylmethane diisocyanate were added and the reaction was carried out at 70 ° C for 8 hours. After the reaction is complete, cool to 40 ° C and use 10% aqueous ammonia.
After 265 parts were added for neutralization, 6090 parts of water was added to solubilize it.

The methyl ethyl ketone was removed from the obtained transparent reaction product at 65 ° C. under reduced pressure, and water was added to adjust the concentration to obtain a stable transparent colloidal dispersion having a nonvolatile content of 25%. The particle size of this product was 0.1 μm or less. 100 this water dispersion
After coating with a solid content of 2 g / m ² on a μm PET film, 100
About the transparent dry film obtained by drying for 1 minute at ℃,
As a result of tests of adhesion, water resistance and blocking resistance, good physical properties were obtained. Furthermore, after applying a magnetic paint, cellophane ink, and an aqueous gelatin solution to the primer-treated resin PET film and allowing it to dry, a peeling test using cellophane tape was performed, and as a result, both the adherend layer and the primer layer peeled from the PET film. It was found that the water-based polyester polyurethane resin of the present invention had excellent adhesiveness without being treated.

Examples 2 to 4 and Comparative Examples 1 to 3 In the same manner as in Example 1, various polyester polyols shown in Table 1 were used to obtain aqueous polyester polyurethane resins of Examples 2 to 4 and Comparative Examples 1 to 3. . Incidentally, Examples 2, 3,
4. In Comparative Examples 1 and 3, urethanization was carried out using 2,2-dimethylolpropionic acid as a chain extender. The physical properties and adhesiveness of each dry film are summarized in Table-2.

In Comparative Example 1, since the content of the aromatic polyester segment was low, the adhesiveness to the PET film was not sufficient, and therefore peeling occurred between the primer layer and the PET film even when the magnetic paint, cellophane, ink or gelatin was applied. Sufficient adhesion cannot be obtained.

In Comparative Example 2, since the content of the aromatic dicarboxylic acid is low, the water resistance and blocking resistance are insufficient and the adhesiveness is also low.

Further, in Comparative Example 6, since the molecular weight of the polyester polyol is low, the resistance to impact peeling is weak and the adhesive strength is also weak. On the other hand, it is recognized that all of the water dispersions of the present invention exhibit excellent physical properties and adhesiveness and are excellent as primer coating agents.

Claims (1)

[Claims] 1. From an acid component (A-1) and a glycol component (A-2) consisting of (A) aromatic dicarboxylic acid / fatty (ring) group dicarboxylic acid = 70/30 to 100/0 (weight ratio) A high-molecular weight product obtained from a polyester polyol having an average molecular weight of 800 to 4000, (B) a polyisocyanate compound, and (C) a chain extender if necessary, in which the pendant carboxyl group is contained in the high-molecular weight product. A primer coating agent, which comprises 0.5 to 6% by weight, and contains an aqueous polyester polyurethane resin in which the carboxyl group is neutralized with ammonia or an organic amine.