JPH0613691B2 - Water-based polyester adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sealing adhesive for imparting heat-sealing property to biaxially stretched polypropylene film and other plastic films, aluminum, paper and the like,
The purpose is to obtain an adhesive that is an alternative to conventional organic solvent type adhesives and that sufficiently satisfies the adhesive strength, blocking resistance, etc. generally required in the market.

Among plastic films used for food packaging such as rice crackers, snacks, dried confectionery and various other packaging, polyethylene film, which has heat sealing property itself, is separated from biaxially oriented polypropylene film, polyester film, etc. Since there is no sealing property, it is necessary to impart heat sealing property. In the case of a stretched polypropylene film, a method of applying a heat-sealing adhesive to the surface or laminating an unstretched polypropylene film on the surface by extrusion is used to impart heat sealability. Currently chlorinated polypropylene, as a heat seal adhesive for coating the surface
Vinyl chloride / vinyl acetate copolymer, vinylidene chloride, etc. are used. Chlorinated polypropylene and vinyl chloride / vinyl acetate copolymer are prepared by dissolving a resin in an organic solvent such as toluene, and an aqueous adhesive is desired from the viewpoint of pollution and fire. Since vinylidene chloride has poor adhesion to a biaxially oriented polypropylene film, it has a drawback that an anchor coating agent must be coated between the polypropylene film and the heat seal adhesive.

The inventors of the present invention have earnestly studied to develop a heat seal adhesive which is water-based and has adhesiveness to a biaxially oriented polypropylene film, and which satisfies the necessary conditions such as heat sealability, blocking resistance, transparency, and moisture resistance. As a result, the present invention has been completed.

The heat-sealable adhesive of the present invention contains (A) a sulfonate and / or a carboxylate in the molecule and has a molecular weight of 250.
0 to 30000 polyester resin, (B) Tg containing acrylate and / or methacrylate in the molecule is 5
105 ° C, preferably 30-80 ° C (meth) acrylic acid ester copolymer resin, (C) water-soluble organic solvent having a boiling point of 60-200 ° C, (D) surfactant and (E) water And the mixing ratio (weight basis) of these components satisfies the following formula.

(A) + (B) + (C) + (D) + (E) = 100 (A) + (B) = 5 to 70 (B) / (A) = 0.01 to 2 (C) = 2 ˜50 (D) = 0.01 to 10 (E) = 15 to 95 The stretched polypropylene film obtained by applying the heat-sealable adhesive of the present invention on the surface and drying the adhesive exhibits an adhesive strength comparable to that of chlorinated polypropylene. Further, the heat-seal adhesive of the present invention has sufficient adhesiveness and therefore can sufficiently oppose the solvent-based heat-seal adhesives used so far. Of course, it can also be used as an anchor coating agent.

The polyester resin used as the component (A) in the present invention has a polycarboxylic acid component containing 30 to 100 mol% of an aromatic dicarboxylic acid containing no sulfonic acid metal base, 70 to 0 mol% of an aliphatic or alicyclic dicarboxylic acid, and a sulfonic acid. A metal base-containing aromatic dicarboxylic acid of less than 30 mol% and a polyol component of an aliphatic glycol or / and an alicyclic glycol having 6 to 12 carbon atoms having a molecular weight of 2500 to
A polyester resin having a carboxyl group concentration of 30,000 and 140 KOH mg / g or less is preferable.

Examples of the aromatic dicarboxylic acid containing no metal sulfonate group include terephthalic acid, isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid. These aromatic dicarboxylic acids containing no metal sulfonate group are used in the range of 30 to 100 of the polycarboxylic acid component.
Must be mol%. If it is less than 30 mol%, the polyester resin is inferior in mechanical strength and weather resistance, which is not preferable.

Examples of the aliphatic or alicyclic dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, dimer acid, tetrahydrophthalic acid, hexahydrophthalic acid, hexahydroisophthalic acid,
Hexahydroterephthalic acid and the like can be mentioned.
The aliphatic or alicyclic dicarboxylic acid is 70 to 0 mol% of the polycarboxylic acid component. If it exceeds 70 mol%, the water resistance and the coating film strength are lowered and the tackiness is exhibited. Further, p-hydroxybenzoic acid, p- (2-hydroxyethoxy) benzoic acid or hydroxypivalic acid, γ-butyrolactone, ε-caprolactone and the like can be used if necessary. If necessary, a tri- or higher functional polycarboxylic acid such as trimellitic acid or pyromellitic acid may be used if it is 10 mol% or less based on all polycarboxylic acid components.

Ethylene glycol, 1,2 as the aliphatic glycol
-Propylene glycol, 1,3-propanediol,
1,4-butanediol, diethylene glycol, neopentyl glycol, 1,5-pentanediol, 1,
6-hexanediol etc. can be mentioned. Examples of the alicyclic glycol having 6 to 12 carbon atoms include 1,4-cyclohexanedimethanol. Carbon number 2
~ 8 aliphatic glycol or / and 6-12 carbon atoms
The alicyclic glycol of 90 to 90% of the total polyol component
It is 100 mol%. If necessary, trifunctional or higher functional polyols such as trimethylolpropane, trimethylolethane, glycerin, and pentaerythritol may be contained in an amount of 10 mol% or less based on all polyol components. Further, if necessary, polyalkylene glycol, particularly polyethylene glycol having a molecular weight of 10,000 or less, may be used as long as it is 20% by weight or less based on all polyol components.
If the amount of polyalkylene glycol, especially polyethylene glycol, exceeds 20% by weight, the water resistance and weather resistance of the polyester resin are extremely lowered.

Examples of the dicarboxylic acid containing a metal sulfonate group include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid,
A metal salt such as 5 [4-sulfophenoxy] isophthalic acid can be used. Metal salts include Li, Na, K, Mg,
Examples include salts of Ca, Cu, Fe and the like. Particularly preferred is 5-sodium sulfoisophthalic acid. The amount of the aromatic dicarboxylic acid containing a metal sulfonate group is less than 30 mol% with respect to the total polycarboxylic acid component, preferably 10 mol% or less with respect to the total polycarboxylic acid component. As the amount of the metal base-containing aromatic dicarboxylic acid increases, good dispersibility is exhibited. However, when it exceeds 30 mol%, the dispersibility of the obtained polyester resin in water itself is good, but the water resistance of the film obtained after coating and drying this is extremely poor.

As the carboxylic acid salt contained in the molecular chain of the polyester resin of the present invention, terephthalic acid, isophthalic acid, orthophthalic acid, trimellitic acid, aromatic polycarboxylic acid such as pyromellitic acid, and further succinic acid, adipic acid, sebacic acid,
Carboxyl groups and Li, Na, introduced intentionally at the end of the molecular chain by aliphatic polycarboxylic acids such as azelaic acid,
Metals such as K, Mg, Ca, Cu, and Fe, as well as ammonia,
Examples thereof include organic salts with amine derivatives such as monomethylamine, dimethylamine, monoethylamine, diethylamine, monoethanolamine and diethanolamine. The carboxyl group concentration of the polyester resin of the present invention is 140 KOH mg / g or less, preferably 84
It is in the range of KOH mg / g or less. 140 carboxyl groups
If it exceeds KOH mg / g, a stable aqueous polyester resin cannot be obtained. As the carboxylic acid salt, any concentration can be used as long as it is 140 KOH mg / g or less.

In the present invention, the polyester resins may be used alone or in combination of two or more if necessary. The molecular weight of the polyester resin of the present invention is in the range of 2,500 to 30,000, and particularly preferably 3,000 to 20,000. When the molecular weight does not reach 2500, the mechanical properties of the obtained film, particularly the flexibility, are deteriorated, which is not preferable. Further, if the molecular weight exceeds 30,000, the viscosity of the aqueous dispersion becomes high, which makes it difficult to increase the content of the polyester resin.

The polyester resin used in the present invention can be produced by any known method. Further, the polyester resin thus obtained can be mixed with an amino resin, an epoxy compound, an isocyanate compound or the like in a molten state or a solution state with a water-soluble organic compound described later. Alternatively, it is possible to carry out a partial reaction with these compounds, and the partial reaction product obtained can also be used as a raw material for an aqueous dispersion.

The acrylic acid ester copolymer resin used as the component (B) in the present invention is preferably 90 mol% or more of acrylic acid ester or / and methacrylic acid ester as a monomer component and 10 mol% or less of acrylic acid salt and / or methacrylate salt. Is a copolymer resin having Tg of 5 to 105 ° C. Examples of the acrylate ester include methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, and examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, butyl methacrylate, and the like. Examples of the acrylate and methacrylate include metal salts such as Li, Na and K, and organic salts such as ammonia, monoethanolamine and diethanolamine.

The water-soluble organic solvent used as the component (C) in the present invention preferably has a solubility in water of 1 at 20 ° C. of 20.
It is an organic solvent of g or more, and specific examples thereof include aliphatic and alicyclic alcohols, ethers, ester and ketone compounds. Specifically, for example, methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, sec-butanol, tert-
Monohydric alcohols such as butanol, glycols such as ethylene glycol and propylene glycol, methyl cellosolve, ethyl cellosolve, n-butyl cellosolve,
tert-butyl cellosolve, 3-methyl-3-methoxybutanol, glycol derivatives such as n-butyl cellosolve acetate, ethers such as dioxane and tetrahydrofuran, esters such as ethyl acetate, methyl ethyl ketone, cyclohexanone, cyclooctanone, cyclodecanone, isophorone Such as ketones. Particularly preferred are n-butyl cellosolve, ethyl cellosolve, isopropanol and the like. These water-soluble organic compounds may be used alone or in combination of two or more. The boiling point of these water-soluble organic solvents needs to be in the range of 60 to 200 ° C. If the boiling point does not reach 60 ° C., it is difficult to maintain a temperature sufficient to mix or dissolve the polyester resin in this organic compound. Furthermore, the boiling point is 20
If the temperature exceeds 0 ° C, rapid drying property cannot be obtained after coating the obtained aqueous dispersion. Further, when an amide-based compound or a sulfonate-based compound is used as the water-soluble compound, the drying property is poor and at the same time the storage stability of the water-based resin is poor.

The adhesive strength of the adhesive of the present invention largely depends on the polyester resin as the component (A). This polyester resin has strong adhesiveness to biaxially oriented polypropylene and other plastics, and rapidly melts at around 100 ° C. to exhibit heat sealability. The acrylic resin as the component (B) has the meaning of improving slipperiness and the effect of improving adhesive strength. The total amount of polyester resin and acrylic resin is 5 to 70 relative to the total amount of adhesive.
% By weight, preferably 10 to 50% by weight, the acrylic / polyester ratio being 0.01 to 2, preferably 0.0.
It is 5 to 0.5. If the acrylic / polyester ratio is less than 0.01, the adhesive strength will decrease, and if it exceeds 2, the adhesive strength and water resistance will decrease. The water-soluble organic solvent as the component (C) has an effect of improving wettability when the adhesive is applied to the film. The mixing ratio is 2 to 50% by weight, preferably 2 to 30% by weight based on the total amount of the adhesive.
The surfactant of the component (D) is also for the purpose of improving wettability. What is contained in this is a nonionic activator and an anionic activator, and especially a fluorine-based activator is effective because the addition amount is small. Cationic activators cannot be used because of poor compatibility with the resin. The mixing ratio is 0.01 with respect to the total amount of adhesive.
10 to 10% by weight, preferably 0.01 to 1% by weight,
If the amount added is too large, the adhesive strength, water resistance, etc. will deteriorate, which is not preferable. The mixing ratio of water as the component (E) is 15 to 95% by weight, preferably 50 to 90% by weight based on the total amount of the adhesive.
% By weight. If it is less than 15% by weight, the viscosity of the water-based polyester-based adhesive becomes high, resulting in poor coatability and poor drying property. On the other hand, if it exceeds 95% by weight, the viscosity becomes low and the desired coating thickness cannot be obtained.

The aqueous polyester heat-seal adhesive of the present invention comprising the mixture of (A) to (E) above is separated with a stable aqueous dispersion,
No precipitation and no change in performance for at least one year. Both gravure coating and doctor coating can be applied to the film, and even if the coating amount is reduced, there will be no flicker and uniform coating will be possible. The dried and wound film exhibits good physical properties in terms of heat seal strength, blocking resistance, transparency, water resistance, slip resistance and the like.
An example will be described below.

Parts in the following production examples are parts by weight.

Measurement method Coating amount Calculated from the weight difference of the film before and after coating Transparency Judgment with the naked eye Heat sealing strength Sealing temperature 120 ° C, sealing pressure 2
Kg / cm ² , sealing time 0.5 seconds Sliding property Judgment by touch Moisture resistance 40 ° C., 90% RH, 24 hours Production Example 1 115 parts of dimethyl terephthalate, 75 parts of dimethyl isophthalate, 71 parts of ethylene glycol, 110 parts of neopentyl glycol, 0.1 part of zinc acetate and 3 parts Charge 0.1 part of antimony oxide into a reaction vessel,
The transesterification reaction was carried out at 0 ° C. for 3 hours. Next, 10.0 parts of 5-sodium sulfoisophthalic acid was added, and the esterification reaction was carried out at 220 to 260 ° C for 1 hour, and then at 240 to 270 ° C under reduced pressure (10 to 0.
2mmHg), polycondensation reaction is carried out for 2 hours, molecular weight 1
A polyester resin (A-1) having a resin content of 3200, a carboxyl group concentration of 3.4 KOH mg / g and a softening point of 157 ° C. was obtained.

Production Example 2 Polycondensation reaction was performed in exactly the same manner as in Production Example 1 except that 38 parts of dimethyl terephthalate, 152 parts of dimethyl isophthalate, 120 parts of ethylene glycol, 85 parts of diethylene glycol, and 10 parts of 5-sodium sulfoisophthalic acid were used to carry out a polycondensation reaction. A polyester resin (A-2) having a softening point of 115 ° C. of 15,000 was obtained.

Example 1 Polyester resin (A-1) as polyester resin
As a water-soluble acrylic resin, methyl methacrylate (M
MA) / methyl acrylate (MA) / methacrylic acid (M
AA) 61/36/3 copolymer, ethyl cellosolve as a water-soluble organic solvent, and Florard FC-129 (a fluorine-based surfactant manufactured by Sumitomo 3M) as a surfactant were used. The acrylic resin / polyester ratio was 0.18, the total amount of acrylic resin and polyester was 15% by weight, ethyl cellosolve was 6.5% by weight, and Florard FC-
129 is 0.1% by weight. Using 28% aqueous ammonia, MMA was changed to ammonium methacrylic acid salt, and the pH of the liquid was adjusted to 8.1. The viscosity was 4 cps.

The above heat-seal adhesive was coated with a Meyer bar No. 8 on a biaxially oriented polypropylene film having a thickness of 20 μm and subjected to a single-sided corona discharge treatment. The coated film was dried with hot air at 80 ° C. for 30 seconds. The heat-sealing strength, anti-blocking property, etc. of the obtained film were measured. The results are shown in the table, which showed good physical properties.

Example 2 Polyester resin (A-2) as the polyester resin
The same acrylic resin as in Example 1 was used as the acrylic resin, and the acrylic resin / polyester ratio was 0.11.
And the total amount of resin was 15% by weight. 5% by weight of isopropanol was used as the water-soluble organic solvent, 0.1% by weight of Florard FC-129 was used as the surfactant, and 28% ammonia water was used to adjust the pH to 8.1.
A was ammonium salt. When this was coated on a biaxially oriented polypropylene film in the same manner as in Example 1 and performance evaluation was performed, good results were obtained.

Production Example 3 115 parts of dimethyl terephthalate, 75 parts of dimethyl isophthalate, 71 parts of ethylene glycol, 110 parts of neopentyl glycol, 0.1 part of zinc acetate and 0.1 part of antimony trioxide were charged into a reactor and 3 at 140 to 220 ° C. The transesterification reaction was carried out over time. Then 24
The polycondensation reaction was carried out at 0 to 270 ° C. under reduced pressure (10 to 1 mmHg) for 30 minutes. Next, under normal pressure 170-190 ℃
Then, 15 parts of trimellitic anhydride was added and the addition reaction was carried out for 30 minutes. A polyester resin having a molecular weight of 2700, a softening point of 95 ° C. and a carboxyl group concentration of 41.5 KOH mg / g (A-
3) was obtained.

Example 3 A biaxially oriented polypropylene film was coated with the same composition and method as in Example 1 except that the polyester resin (A-3) was used as the polyester resin, and the performance of the obtained film was evaluated. Results were obtained.

Comparative Example 1 15% by weight of polyester in a mixed aqueous solution of polyester resin (A-1), ethyl cellosolve and Florard FC-129, 6.5% by weight of ethyl cellosolve, Florard FC-
The heat seal adhesive was adjusted so that 129 was 0.1% by weight. This was processed into a biaxially oriented polypropylene film in the same manner as in Example 1 and the performance of the obtained film was evaluated. The transparency, blocking resistance, and moisture resistance were the same as those of the example, but the heat seal strength was slightly weaker than that of the example 1, and the slip property was poor.

Comparative Example 2 A heat seal adhesive was prepared in the same composition as in Example 1 except that Florard FC-129 was excluded from the composition of Example 1, and an attempt was made to apply it to a biaxially oriented polypropylene film. It could not be applied evenly.

Comparative Example 3 The amount of ethyl cellosolve in the composition of Example 1 was 1.5% by weight.
An adhesive was prepared with the same composition as in Example 1 except that the coating was applied to a biaxially oriented polypropylene film, but the coating was repelled in a small coating amount range of 1 g / m ² or less. .

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Koji Takeuchi 2-1-2 Katata, Otsu City, Shiga Prefecture

Claims (1)

[Claims] 1. A polyester resin having a molecular weight of 2,500 to 30,000 containing (A) a sulfonate and / or a carboxylate in the molecule, and (B) a Tg containing an acrylate and / or a methacrylate in the molecule. An aqueous solution comprising a mixture of (meth) acrylic acid ester copolymer resin of 5 to 105 ° C., (C) a water-soluble organic solvent having a boiling point of 60 to 200 ° C., (D) a surfactant, and (E) water, and An aqueous polyester-based adhesive in which the mixing ratio of (A), (B), (C), (D) and (E) satisfies the following formula in weight ratio. (A) + (B) + (C) + (D) + (E) = 100 (A) + (B) = 5 to 70 (B) / (A) = 0.01 to 2 (C) = 2 -50 (D) = 0.01-10 (E) = 15-95