JPH0323585B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention has a high solid content and low viscosity during processing,
The present invention also relates to an adhesive composition for dry laminated films, which has a stable pot life and has excellent properties such as fast curing and good adhesiveness. [Prior Art] Dry lamination is a technology that has the great feature of being able to freely bond arbitrary films to each other using an adhesive, and producing high-performance packaging materials tailored to the purpose. In this dry lamination, organic solvent-based polyurethane adhesives are used in most cases because of their ease of use, excellent adhesive performance, and excellent durability. When laminating, the adhesive is diluted with an organic solvent to have a solid content of about 20 to 35% before being coated on the film. That is, the organic solvent corresponding to 65 to 80% of the adhesive composition is discharged into the atmosphere. [Problems to be Solved by the Invention] Accordingly, dry lamination using organic solvent adhesives faces the following problems, and countermeasures are required. (1) Regulation of organic solvent emissions (for pollution prevention) (2) Resource and energy conservation (3) Improvement of factory working environment (for occupational safety and health) (4) Control of residual solvents in laminate films (for food safety and health) As a solution to these problems, attempts have been made to reduce the amount of organic solvent, such as making it water-based, making it solvent-free, and increasing its solid content. Among these, adhesives that can be processed with a high solids content are developed by reducing the organic solvent content by increasing the solid content ratio during application of solvent-based adhesives, which is conventionally about 20 to 35%. This is an attempt to solve the problems of The higher the solid content ratio of the adhesive during lamination, the more the amount of organic solvent discharged will be reduced. The effects obtained by this are as follows. (1) Solvent costs can be reduced. (2) By reducing the drying load, productivity can be improved and energy costs can be reduced. (3) Less residual solvent. However, technical problems arising from increasing the solid content ratio of adhesive during lamination processing include: (1) The pot life is shortened, so the solution viscosity tends to increase, making it difficult to apply the adhesive uniformly. It is difficult to control the coating amount. (2) By lowering the viscosity of the adhesive (lowering the molecular weight) in order to make it coatable, the curing speed of the adhesive tends to slow down. etc. As a result of intensive research into high solid content type adhesives, the present inventors discovered an adhesive composition for laminated films that solves these problems and completed the present invention. [Means for Solving the Problems] In order to solve the above problems, the present inventors have developed a method comprising the (A) trihydric alcohol of the present invention, a polyether polyol, a polyester polyol, and a polyether polyester polyol. one or more polyols selected from the group;
Consisting of polyisocyanates, 2-15% free
A urethane prepolymer component containing an NCO group (hereinafter referred to as prepolymer (A)) and (B) 400~
Polyether polyol having a number average molecular weight of 4000 and 3 or more hydroxyl groups in the molecule and/or 300
In a laminating adhesive composition comprising a polyester polyol component having a number average molecular weight of ~2000 and two or more hydroxyl groups in the molecule, the equivalent weight of free isocyanate groups (-NCO) in the component (A) is 1.0 equivalent of hydroxyl group (-OH) in component (B)
Provided is an adhesive composition for laminate film, characterized in that the adhesive composition is increased by ~5.0 times. Examples of the trihydric alcohol as component (A) used in the present invention include trimethylolpropane, glycerin, trimethylolethane, and 1,2,6-hexanetriol. Examples of the polyether polyol as component (A) used in the present invention include linear or branched polyalkylene polyols such as polyethylene glycol, polypropylene glycol, glycerin, or ethylene oxide or propylene oxide adducts of trimethylolpropane. Can be mentioned. As the polyester polyol of component (A) used in the present invention, a linear or branched polyester having an OH group in the molecular chain obtained by reacting a polybasic acid with a low molecular weight polyol can be used, Examples of the polybasic acid include adipic acid,
Dibasic acids or their esters such as azelaic acid, dodecanedioic acid, dimer acid, isophthalic acid, hexahydrophthalic anhydride, terephthalic acid, dimethyl terephthalate, itaconic acid, fumaric acid, maleic anhydride, hexahydrophthalic anhydride; trimeric anhydride Examples include tribasic acids such as acids. In addition, examples of the low-molecular polyol include ethylene glycol, butylene glycol,
Examples include diols such as diethylene glycol and hydrogenated bisphenol A; triols such as glycerin and trimethylolpropane; and polyols having four or more functionalities such as pentaerythritol and sorbitol. Further, a ring-opening polymer of ()ε-caprolactone and a di- to trifunctional polyester polyol can also be used. The polyether polyester polyol as component (A) used in the present invention includes () a molecular chain obtained by esterifying the polybasic acid and the polyether polyol, or a mixture of this and the low-molecular polyol; Obtained by adding alkylene oxide (e.g. ethylene oxide, propylene oxide, etc.) to a linear or branched polyester having an OH group therein, or a polyester having a carboxyl group and/or a hydroxyl group at the end. Polyether, ()ε−
A copolymer of caprolactone ring-opening polymer and polypropylene glycol and/or polytetramethylene glycol can be used. Examples of the 3-polyisocyanate as component (A) used in the present invention include hexamethylene diisocyanate, o-, m- or p-phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate, and polyisocyanate in which the aromatic ring is hydrogen. Added 2,4- or 2,6-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, dicyclohexylmethane-
4,4'-diisocyanate, isophorone diisocyanate, ω,ω'-diisocyanate-1,4
-dimethylbenzene and ω,ω'-diisocyanate-1,3-dimethylbenzene, which can be used alone or in combination. Furthermore, examples of the low-molecular polyol used as necessary in the production of the prepolymer (A) include the low-molecular polyols listed as raw materials for the polyester polyol. In addition, prepolymer
In the production of (A), amino alcohols such as ethanolamine and propanolamine, amino compounds such as ethylenediamine and n-butylamine, water, etc. may be used. The urethanization reaction in producing the prepolymer (A) may be carried out usually at a reaction temperature of 50 to 100°C in the presence or absence of an organic solvent inert to isocyanate groups. In addition, when performing the urethanization reaction,
If desired, as a catalyst, for example, dibutyltin dilaurate, stannath-2-ethylhexoate iron-acetylacetonate, triethylenediamine, N-methylmorpholine, etc. may be added in an amount of 0.005 to 0.2% by weight based on the resin solid content. The prepolymer (A) having terminal isocyanate groups produced in this manner suitably has 2 to 15% of free isocyanate groups, more preferably 3 to 15% of free isocyanate groups.
Those with 10% free isocyanate groups are suitable. When the content of free isocyanate groups is less than 2%, the viscosity of the prepolymer becomes high, making it difficult to process with a high solids content. Moreover, when it exceeds 15%, the cured adhesive coating becomes hard and the adhesiveness decreases. The polyether polyol as component (B) used in the present invention is, for example, a polyol having three or more hydroxyl groups in the molecule, such as glycerin or trimethylolpropane, reacted with ethylene oxide or propylene oxide. Examples include polyether polyols having three or more hydroxyl groups. For number average molecular weight, 400~
4000 is preferred. If the number average molecular weight is less than 400, the amount (% by weight) of the component (A) to be blended will be small, which will increase the viscosity of the adhesive composition, which is not preferable. In addition, the reaction is rapid, the pot life is short, and processing with a high solids content is difficult.
When the number average molecular weight exceeds 4000, the crosslinking density after curing becomes small, and adhesion tends to occur, resulting in poor adhesive strength and
Boil resistance, heat resistance, etc. deteriorate, which is not preferable. The polyester polyol of component (B) used in the present invention may be any polyester polyol having two or more hydroxyl groups in the molecule, but in particular it consists of a polyester polyol having three hydroxyl groups in the molecule as a main component. The case is most preferred. The number average molecular weight is preferably 300 to 2000. Examples of the polyester polyol as the component (B) include the polyester polyol as the component (A). It is also possible to add 0 to 20% of an epoxy resin and 0 to 10% of a silane coupling agent to component (B). Regarding the mixing ratio of components (A) and (B), the equivalent of isocyanate groups in component (A) is equal to the equivalent of hydroxyl groups in component (B).
It is preferably 1.0 to 5.0 times, more preferably 1.5 to 3.5 times. The solvent added to the adhesive composition of the present invention includes:
Any organic solvent may be used as long as it does not show reactivity with isocyanate groups or hydroxyl groups, and examples include aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate; and ketones such as acetone and methyl ethyl ketone. . The solvent may be added to component (A) or component (B) in advance, or may be added at the time of mixing component (A) and component (B). To perform lamination using the adhesive composition for laminate films of the present invention, the adhesive is applied to the film surface using a commonly used method, for example, using a dry laminator, the solvent is evaporated, and then, A method is employed in which the adhesive surfaces are brought together and the composition is cured at room temperature or under heating. As is clear from the examples described later, the adhesive composition for laminating films of the present invention has good adhesive properties as a laminating adhesive for polypropylene, polyethylene, nylon, polyethylene terephthalate, Al-deposited film, paper aluminum foil, etc. Furthermore, it can be processed with a high solid content, has a long pan life and pot life, and hardens quickly after lamination. The present invention will be specifically described below with reference to Examples. All "%" in Examples means "% by weight". [Example] 1 Synthesis of urethane prepolymer containing terminal isocyanate groups of component (A) Tolylene diisocyanate (TDI) (2,4/
Heat 522 g of 2,6-isomer weight ratio = 80/20) and 780 g of ethyl acetate to 60°C, and add 92 g of glycerin.
was gradually added and allowed to react for 4 hours. after that,
Add 226 g of TDI and 1500 g of polypropylene glycol with a number average molecular weight of 1000, and
Allowed time to react. This polyurethane prepolymer solution (hereinafter referred to as prepolymer A-)
The solid content was 75%, the NCO group content was 3.5% (4.7% based on the solid content), and the viscosity was 2000 cps/25°C. (2) TDI 244g, ethyl acetate 167g, polypropylene glycol 100 with a number average molecular weight of 1000
Heat g to 60℃ and add 54 g of trimethylolpropane.
g was gradually added, and the mixture was allowed to react for 6 hours. after that,
113 g of TDI, 110 g of polypropylene glycol having a number average molecular weight of 1000, and 47 g of ethylene glycol were added and reacted at 75° C. for 8 hours. This polyurethane prepolymer solution (hereinafter referred to as A-
Say. ) has a solid content of 80% and an NCO group content of 8.
% (10% based on solid content), viscosity is 2300cps/
It was 25℃. (3) 522 g of TDI and 627 g of ethyl acetate were heated to 60°C, 134 g of trimethylolpropane was gradually added, and the mixture was reacted for 4 hours. After that, TDI226g,
1000 g of bifunctional polycaprolactone polyol ("Plaxel 208" manufactured by Daicel Chemical Industries, Ltd.) was added and reacted at 70° C. for 5 hours. This polyurethane prepolymer solution (hereinafter referred to as prepolymer A-
Say. ) is 75% solids, NCO content 4.9
% (6.5% based on solid content), viscosity 3000cps/25
It was warm at ℃. 2 (B) Component polyether triol

【table】 3 (B) Component polyester polyol

[Table] Polyurethane prepolymers A-, A- and A-, polyether polyols and polyester polyols B-1, B-2, B-3 and B-
4 to prepare laminate film adhesive compositions No. 1 to No. 6 shown in Table 1.

[Table] The "NCO/OH" column in Table 1 shows the value obtained by dividing the number of equivalents of free isocyanate groups (-NCO) in the prepolymer by the number of equivalents of hydroxyl groups (-OH) in the polyol. be. The above adhesive composition for laminate film was diluted with ethyl acetate, and the viscosity and pot life at a solid content of 50% are shown in Table 2.

[Table] As is clear from Table 2, the adhesive composition for laminated films of the present invention has a low viscosity of 16 to 28 seconds at a solid content of 50%, and a small increase in viscosity even when kept at 40°C. Pot life is stable. In addition, in the case of normal dry lamination processing, the solid content of the adhesive is 20 to 35%, and a viscosity in the range of 10 to 30 seconds (Zahn Cup No. 3) interferes with workability and the appearance of the laminated film. This is a condition where no Next, each of the adhesive compositions for laminate films of the present invention was diluted with ethyl acetate to adjust the solid content to 50%. Using a regular dry laminator,
Various films were laminated and the curing speed and adhesive strength were measured. The commercially available adhesive composition for laminate film shown below was used as a comparative example to clarify the technical effects of the present invention. Commercial products used: 2 parts of "EPS781" (polyether polyurethane polyol adhesive manufactured by Dainippon Ink & Chemicals Co., Ltd.) and 2 parts of "KA80" (polyether polyurethane polyisocyanate adhesive manufactured by Dainippon Ink & Chemicals Co., Ltd.) An adhesive composition consisting of 1 part of adhesive composition was diluted with ethyl acetate, and the solid content was adjusted to 25% before use. Γ curing speed stretched nylon film (thickness 15μ) (hereinafter referred to as Ny1
Say. ) and a linear low-density polyethylene film (thickness 60μ) (hereinafter referred to as L-LDPE) were laminated together with each adhesive composition applied at a rate of 2.2 g/m ² to form a laminate film. After that, it was placed in a constant temperature bath at 20°C, and bags were made after 24 hours, 48 hours, and 72 hours. The container was filled with water and a mixture of water and salad oil at a ratio of 10:1. This bag at 98℃
A 1-hour boil test was carried out, and Ny1 and L-LDPE
The curing speed of each adhesive composition was determined by examining the peeling state between the adhesive composition and the adhesive composition. Table 3 shows the results.
It was shown to.

[Table] As is clear from Table 3, the adhesive composition for laminate films of the present invention has boiling resistance even when aged at 20° C. for 24 to 48 hours, and has a fast curing speed. Γ Adhesive strength 300% from a laminated film made in the same manner as above and having the film composition shown in Table 4.
A test piece with a size of mm x 15 mm was taken. Using these test pieces, the adhesive strength was measured by T-peel using an Instron type tensile tester at a peel strength of 300 mm/min. The measured value is the adhesive strength (g/15 mm) between each constituent film as the average value of five test pieces.

【table】

〔Effect of the invention〕

The adhesive composition for laminate films of the present invention has relatively low viscosity even with a high solids content, has a stable pot life, and has excellent effects on curing speed and adhesive strength. Therefore, by using the adhesive composition for laminate films of the present invention, it is possible to reduce solvent costs and drying energy costs, improve productivity, and also reduce the amount of solvent remaining in the laminate film.

Claims (1)

[Claims] 1 (A) a trihydric alcohol, and one or more polyols selected from the group consisting of polyether polyols, polyester polyols, and polyether polyester polyols;
Consisting of polyisocyanates, 2-15% free
(B) a polyether polyol having a number average molecular weight of 400 to 4000 and 3 or more hydroxyl groups in the molecule; and/or a polyether polyol having a number average molecular weight of 300 to 2000 and 2 or more hydroxyl groups in the molecule; In a laminating adhesive composition comprising a polyester polyol component having at least 1 hydroxyl group, the equivalent of the free isocyanate group (-NCO) in the component (A) is equal to the equivalent of the hydroxyl group (-OH) in the component (B). An adhesive composition for laminating film, characterized in that the adhesive composition is 1.0 to 5.0 times the equivalent weight of .