WO2023074667A1 - Adhesive for laminates - Google Patents

Adhesive for laminates Download PDF

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Publication number
WO2023074667A1
WO2023074667A1 PCT/JP2022/039668 JP2022039668W WO2023074667A1 WO 2023074667 A1 WO2023074667 A1 WO 2023074667A1 JP 2022039668 W JP2022039668 W JP 2022039668W WO 2023074667 A1 WO2023074667 A1 WO 2023074667A1
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WO
WIPO (PCT)
Prior art keywords
adhesive
laminates
films
present
laminates according
Prior art date
Application number
PCT/JP2022/039668
Other languages
French (fr)
Inventor
Kenji Matsuda
Original Assignee
Henkel Ag & Co. Kgaa
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Filing date
Publication date
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Publication of WO2023074667A1 publication Critical patent/WO2023074667A1/en

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J175/00—Adhesives based on polyureas or polyurethanes; Adhesives based on derivatives of such polymers
    • C09J175/04—Polyurethanes
    • C09J175/08—Polyurethanes from polyethers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/30—Low-molecular-weight compounds
    • C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
    • C08G18/3203—Polyhydroxy compounds
    • C08G18/3215—Polyhydroxy compounds containing aromatic groups or benzoquinone groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/30—Low-molecular-weight compounds
    • C08G18/36—Hydroxylated esters of higher fatty acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/4009—Two or more macromolecular compounds not provided for in one single group of groups C08G18/42 - C08G18/64
    • C08G18/4018—Mixtures of compounds of group C08G18/42 with compounds of group C08G18/48
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
    • C08G18/4236—Polycondensates having carboxylic or carbonic ester groups in the main chain containing only aliphatic groups
    • C08G18/4238—Polycondensates having carboxylic or carbonic ester groups in the main chain containing only aliphatic groups derived from dicarboxylic acids and dialcohols
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/48—Polyethers
    • C08G18/4825—Polyethers containing two hydroxy groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/48—Polyethers
    • C08G18/4829—Polyethers containing at least three hydroxy groups

Definitions

  • the present invention relates to an adhesive for laminates. More particularly, the present invention relates to: an adhesive for laminates, which is excellent in stability and adhesion and does not degrade the appearance of films when bonding a plurality of films together; and a laminated film using the same.
  • Plastic films e.g., films made of polyethylene, polypropylene, nylon, polyester, polyimide, or the like
  • metal vapor-deposited films e.g., foils made of aluminum, copper, or the like
  • substrates such as FPC substrates and TAB substrates.
  • adhesives for bonding these plastic films metal vapor-deposited films, metal foils and the like, urethane adhesives containing a combination of an organic polyol and an organic isocyanate are known.
  • the solvent-free adhesives are advantageous in that they do not use any solvent; however, they are poor in wettability and are likely to cause generation of voids on the film surfaces at the time of bonding a plurality of films together, which may degrade the appearance of the films. Particularly, defective appearance often occurs in polyethylene terephthalate films on which aluminum is vapor-deposited.
  • PTLs 1 to 3 disclose laminated films that are laminated using an urethane adhesive.
  • PTL 1 discloses: a urethane adhesive composition obtained by mixing a polyisocyanate and a polyol with an ester that is liquid at 25°C; and a laminate obtained by applying the composition (see [Claims] and [Table 1] to [Table 6] of PTL 1).
  • PTL 2 discloses a solvent-free laminate adhesive that contains a polyisocyanate, a polyol, and castor oil (or a castor oil derivative) (see [Claims], [Table 1], and [Table 2] of PTL 2).
  • PTL 3 discloses a one-part liquid adhesive (one-pack type adhesive or one-component type adhesive) that contains a polyester-based urethane resin, a specific polyol, and a polyisocyanate (see [Claims] of PTL 3).
  • Table 4 of PTL 3 discloses adhesives that contain a polyester-based urethane resin, a rosin ester, and diphenylmethane diisocyanate (see [Claim 4] and [Table 4] of PTL 3).
  • PTLs 1 to 3 describe that the respective adhesives improve the appearance of a laminated film (see PTL 1 [0017], PTL 2 [0015], and PTL 3 [0005]); however, they cannot be said to sufficiently satisfy the high demand of consumers. Further, in consideration of the working efficiency in the production of a packaging bag using the laminated film, the adhesive is desired to have an excellent compatibility of its components as well as an excellent adhesive strength to films after curing.
  • the present invention was conceived to solve the above-described problems, and an object of the present invention is to provide: an adhesive for laminates which, in the production of a laminated film by laminating plastic films, exhibits an excellent adhesive strength to the films after curing and an excellent compatibility of components, allows efficient coating process and film production without degrading the appearance of the laminated film, and has an excellent balance of these properties; and a laminated film produced using the adhesive for laminates, which laminated film has an excellent appearance and an excellent balance of the above-described properties.
  • a urethane resin composition which contains a urethane prepolymer, a polyether polyol, and a specific phenol-based compound not only is excellent in compatibility of components and has an excellent adhesive strength to films in the production of a laminated film by lamination of plastic films, but also exhibits an excellent balance of these properties without degrading the appearance of the resulting laminated film, thereby completing the present invention.
  • An adhesive for laminates comprising: (A) a urethane prepolymer having an isocyanate group at the end; and (B) a phenol-based compound derived from a cashew nut shell liquid (CNSL). 2.
  • the adhesive for laminates according to 1 or 2 wherein the adhesive comprises the component (B) in an amount of 5 to 70 parts by mass per 100 parts by mass of the total mass of the components (A) and (B).
  • the natural resin comprises a rosin ester.
  • the adhesive for laminates according to one embodiment of the present invention contains (A) a urethane prepolymer having an isocyanate group at the end and (B) a phenol-based compound derived from a cashew nut shell liquid (CNSL); therefore, the adhesive for laminates is excellent in compatibility and adhesive strength, and has an excellent balance of these properties.
  • CNSL cashew nut shell liquid
  • FIG. 1 schematically illustrates a cross-section of a laminated film according to one embodiment of the present invention.
  • FIG. 2 schematically illustrates a cross-section of a laminated film according to another embodiment of the present invention.
  • the adhesive for laminates according to one embodiment of the present invention contains (A) a urethane prepolymer having an isocyanate group at the end (hereinafter, also referred to as “component (A)”) and (B) a phenol-based compound derived from a cashew nut shell liquid (CNSL) (hereinafter, also referred to as “component (B)”).
  • component (A) a urethane prepolymer having an isocyanate group at the end
  • component (B) a phenol-based compound derived from a cashew nut shell liquid (CNSL)
  • component (C) a polyether polyol
  • component (D) a tackifier resin
  • the adhesive for laminates according to one embodiment of the present invention contains the component (A) and the component (B), and may contain at least one selected from the component (C) and the component (D).
  • the adhesive according to one embodiment of the present invention is not particularly limited in terms of the order, the method, and the like of blending the components (A) to (D) (the components (A) and (B), and the components (C) and (D) that may be blended) as long as an intended adhesive can be obtained.
  • the adhesive according to one embodiment of the present invention can be obtained by, for example, simultaneously blending the (A) urethane prepolymer, the (B) phenol-based compound derived from a cashew nut shell liquid, the (C) polyether polyol, and the (D) tackifier resin; however, the adhesive according to one embodiment of the present invention is more preferably obtained by mixing the components (B) and (C) in advance and subsequently blending the resulting mixture with the component (A).
  • the production of the adhesive by blending (or mixing) of the components (A) to (D) can be carried out by any known method.
  • the adhesive can be obtained by blending the components (A) to (D) in a solvent, or the components (A) to (D) can be blended with each other without using a solvent.
  • the adhesive according to one embodiment of the present invention may be a two-part liquid adhesive, and this two-part liquid adhesive may be one obtained from a first liquid containing the component (A) and a second liquid containing the component (B), one obtained by blending a first liquid containing the component (A) with a second liquid containing the components (B), (C), and (D), or one obtained by blending a first liquid containing the components (A) and (D) with a second liquid containing the components (B) and (C).
  • the adhesive according to one embodiment of the present invention is more preferably a two-part liquid adhesive that contains a first liquid containing the component (A) and a second liquid containing the components (B), (C), and (D).
  • the first liquid and the second liquid may each further contain the below-described various additives and the like as appropriate.
  • the (A) urethane prepolymer is a product of a reaction between (a1) a polyol and (a2) an isocyanate monomer.
  • the number average molecular weight of the (A) urethane prepolymer may be, for example, 400 to 20,000, and it is preferably 1,000 to 10,000, particularly preferably 1,500 to 4,000. When the number average molecular weight of the (A) urethane prepolymer is in this range, the adhesive for laminates according to one embodiment of the present invention exhibits superior adhesion.
  • the number average molecular weight (Mn) is a value that is measured by gel permeation chromatography (GPC) and converted using a polystyrene standard. Specifically, this value can be measured using the following GPC apparatus and measurement method and then converted.
  • GPC apparatus HCL-8220GPC manufactured by Tosoh Corporation is used as a GPC apparatus, and RI is used as a detector.
  • GPC columns two TSKgel SuperMultipore HZM columns manufactured by Tosoh Corporation are used. A sample is dissolved in tetrahydrofuran, and the resulting solution is applied to the columns at a flow rate of 0.35 ml/min and a column temperature of 40°C to obtain a measurement value.
  • This measurement value is converted based on a calibration curve prepared using a polystyrene having a monodisperse molecular weight as a standard substance, whereby the objective Mn is determined.
  • Mn the Mn of the below-described (a1) polyol and the Mn of the below-described (a2) isocyanate monomer.
  • (a1) polyol is a general term for a compound having two or more hydroxy groups in one molecule, and examples thereof include polyether polyols, polyester polyols, acrylic polyols, polycaprolactone polyols, and polycarbonate polyols.
  • the type of the (a1) polyol is not limited as long as the adhesive according to one embodiment of the present invention can be obtained.
  • the number average molecular weight of the (a1) "polyol” may be, for example, 100 to 4,000, and it is preferably 400 to 2,000.
  • the (a1) polyol has a short chain length and is thus likely to crosslink with the (a2) isocyanate monomer. This leads to a further reduction in the amount of unreacted (a2) isocyanate monomer; therefore, the adhesive for laminates according to one embodiment of the present invention contains a greater amount of the (A) urethane prepolymer and exhibits superior adhesion.
  • the (a2) isocyanate monomer is not particularly limited as long as the adhesive for laminates that is intended by the present invention can be obtained; however, the (a2) isocyanate monomer preferably contains an aromatic isocyanate.
  • the adhesion of the adhesive for laminates according to one embodiment of the present invention is further improved.
  • the "(a2) isocyanate monomer” is not meant to consist of an aromatic isocyanate.
  • the (a2) isocyanate monomer may also contain an aliphatic isocyanate and/or an alicyclic isocyanate within a range that does not adversely affect the adhesion of the adhesive for laminates according to one embodiment of the present invention and the appearance of a film.
  • aliphatic isocyanate refers to a compound having a chain-like hydrocarbon chain to which an isocyanate group is directly bound, and the compound does not have a cyclic hydrocarbon chain.
  • the "aliphatic isocyanate” may have an aromatic ring; however, the aromatic ring and the isocyanate group are not directly bound to each other. It is noted here that, in the present specification, an aromatic ring is not included in the cyclic hydrocarbon chain.
  • alicyclic isocyanate refers to a compound which has a cyclic hydrocarbon chain and optionally has a chain-like hydrocarbon chain.
  • An isocyanate group may be directly bound to the cyclic hydrocarbon chain, or may be directly bound to the optional chain-like hydrocarbon chain.
  • the "alicyclic isocyanate” may have an aromatic ring; however, the aromatic ring and the isocyanate group are not directly bound to each other.
  • aromatic isocyanate refers to a compound having an aromatic ring to which an isocyanate group is directly bound. Accordingly, a compound in which an isocyanate group is not directly bound to an aromatic ring is classified as either an aliphatic isocyanate or an alicyclic isocyanate, even if the compound has an aromatic ring in its molecule.
  • 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate correspond to aromatic isocyanates since isocyanate groups are each directly bound to an aromatic ring in these compounds.
  • xylylene diisocyanate (OCN-CH 2 -C 6 H 4 -CH 2 -NCO) corresponds to an aliphatic isocyanate since it has an aromatic ring but isocyanate groups are not directly bound to the aromatic ring and are each bound to a methylene group.
  • the aromatic ring may be a fused ring of two or more benzene rings.
  • aromatic isocyanate examples include 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate.
  • aliphatic isocyanate examples include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (hereinafter also referred to as "HDI"), 1,6-diisocyanato-2,2,4-trimethylhexane, methyl 2,6-diisocyanatohexanoate (lysine diisocyanate), and 1,3-bis(isocyanatomethyl)benzene (xylylene diisocyanate).
  • HDI 1,6-diisocyanatobutane
  • 1,5-diisocyanatopentane 1,6-diisocyanatohexane
  • HDI 1,6-diisocyanato-2,2,4-trimethylhexane
  • methyl 2,6-diisocyanatohexanoate methyl 2,6-diisocyanatohexanoate
  • alicyclic isocyanate examples include 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane (isophorone diisocyanate: IPDI), 1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated xylylene diisocyanate), bis(4-isocyanatocyclohexyl)methane (hydrogenated diphenylmethane diisocyanate), and 1,4-diisocyanatocyclohexane.
  • IPDI isophorone diisocyanate
  • IPDI 1,3-bis(isocyanatomethyl)cyclohexane
  • hydroxylylene diisocyanate bis(4-isocyanatocyclohexyl)methane
  • 1,4-diisocyanatocyclohexane examples include 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane
  • a method of performing the reaction between the (a1) polyol and the (a2) isocyanate monomer is not limited as long as the (A) urethane prepolymer according to one embodiment of the present invention can be obtained, and any general urethanization method may be employed. For example, bulk polymerization using no solvent and solution polymerization using a solvent can be employed. The resultant is heated and stirred as appropriate, and a catalyst may be used as required. Further, there is no problem in using various additives during the reaction between the (a1) polyol and the (a2) isocyanate monomer. Examples of a commercially available product of the (A) urethane prepolymer include LOCTITE LIOFOL LA Series manufactured by Henkel Japan Ltd.
  • the adhesive for laminates contains (B) a phenol-based compound derived from a cashew nut shell liquid.
  • phenol-based compounds may be used singly, or in combination.
  • the component (A) since the (B) phenol-based compound reacts with the isocyanate group contained in the component (A), the component (A) hardly reacts with the moisture in the air.
  • the component (A) is likely to react with the component (B) at the time of bonding films together, so that voids are unlikely to be formed between the films.
  • the "cashew nut shell liquid” refers to a liquid that contains a phenol-based compound collected from shells encapsulating cashew nuts.
  • phenol-based compound examples include anacardic acid, cardanol, cardol, and 2-methylcardol. The chemical structures of these compounds are shown below.
  • R is a hydrocarbon group represented by C 15 H n (wherein, n represents an integer of 19 to 31), and n is preferably an integer of 25 to 31.
  • R may be C 15 H 25 , C 15 H 27 , C 15 H 29 , C 15 H 31 , or a combination thereof.
  • R may be, for example, the following mixture.
  • a natural CNSL contains anacardic acid as a main component.
  • This CNSL is heated when industrially utilized, and anacardic acid is decarboxylated into cardanol. Therefore, an industrial CNSL contains cardanol as a main component.
  • the adhesive for laminates according to one embodiment of the present invention preferably contains a cardanol derivative as the (B) phenol-based compound derived from a cashew nut shell liquid.
  • cardanol derivative used herein refers to a compound having a chemical structure derived from cardanol, and specific examples thereof include a cardanol monomer, a cardanol polymer (polymer based on a cardanol monomer), and a cardanol modification product (a modification product obtained by partial substitution of the chemical structure of cardanol with other functional group).
  • the adhesive for laminates according to one embodiment of the present invention when it contains a cardanol derivative, can further improve the appearance of films that are bonded together.
  • a commercially available product can be used as the cardanol derivative.
  • Examples of a commercially available product of a cardanol polymer include NX9201LP (CNSL polyester, manufactured by Cardolite Japan Ltd.), NX9001LV (CNSL novolac, manufactured by Cardolite Japan Ltd.), and NX9016 (CNSL novolac, manufactured by Cardolite Japan Ltd.).
  • the adhesive for laminates according to one embodiment of the present invention contains the component (B) in an amount of preferably 5 to 70 parts by mass, more preferably 5 to 60 parts by mass, most preferably 10 to 60 parts by mass, per 100 parts by mass of the total mass of the components (A) and (B).
  • the adhesive for laminates according to one embodiment of the present invention contains the component (B) at the above-described ratio, the adhesive can have an improved compatibility of components and an improved adhesive strength while further reducing the amount of voids generated at the time bonding films together and thereby improving the appearance of the films.
  • the adhesive for laminates according to one embodiment of the present invention may further contain (C) a polyether polyol.
  • the "(C) polyether polyol” usually refers to a compound understood as a polyether polyol, and is not particularly limited as long as the adhesive for laminates that is intended by the present invention can be obtained.
  • the (C) polyether polyol include polyethylene glycols (PEG), polyoxytetramethylene glycols (PTMG), and polypropylene glycols (PPG).
  • PEG polyethylene glycols
  • PTMG polyoxytetramethylene glycols
  • PPG polypropylene glycols
  • the (C) polyether polyol can be used singly, or in combination.
  • the (C) polyether polyol is produced by, for example, addition polymerization of an alkylene oxide, such as propylene oxide or ethylene oxide, with a low-molecular-weight compound having two or more hydroxy groups in the molecule, such as propylene glycol, glycerin, sorbitol or sucrose, and/or a polyamine.
  • an alkylene oxide such as propylene oxide or ethylene oxide
  • a low-molecular-weight compound having two or more hydroxy groups in the molecule such as propylene glycol, glycerin, sorbitol or sucrose, and/or a polyamine.
  • an increase in viscosity is inhibited and superior compatibility of components is obtained by incorporating the (C) polyether polyol, and this contributes to an improvement in the adhesive strength.
  • the (C) polyether polyol preferably contains a polypropylene glycol having a number average molecular weight of 300 to 2,000.
  • the adhesive for laminates according to one embodiment of the present invention not only has excellent compatibility of components and is more suitable for a film coating process in the production of a laminated film, but also has a further improved adhesive strength.
  • the adhesive for laminates according to one embodiment of the present invention may contain the (C) polyether polyol in an amount of 0 to 50 parts by mass, preferably 5 to 40 parts by mass, more preferably 5 to 30 parts by mass, per 100 parts by mass of the total mass of the components (A) and (B).
  • the adhesive for laminates according to one embodiment of the present invention can have superior compatibility and adhesive strength.
  • the adhesive for laminates preferably contains (D) a tackifier resin.
  • the adhesive for laminates according to this embodiment of the present invention exhibits a superior adhesive strength and further improves the appearance of films at the time of bonding the films together.
  • Examples of the (D) tackifier resin include styrene-based resins, terpene-based resins, aliphatic petroleum resins, aromatic petroleum resins, rosin esters, acrylic resins, and polyester resins (excluding polyester polyols), and the (D) tackifier resin preferably has a softening point of 80 to 120°C.
  • the adhesive for laminates according to one embodiment of the present invention not only can maintain a more appropriate hardness and has a superior adhesive strength, but also can further inhibit the generation of voids and thereby further improve the appearance of films when applied to the films.
  • the tackifier resin a commercially available product can be used.
  • the (D) tackifier resin preferably contains a rosin ester.
  • the adhesive for laminates according to one embodiment of the present invention contains a rosin ester, the compatibility of components is further improved, so that the adhesive strength is further improved.
  • Examples of rosin generally include natural rosin, modified rosin, and hydrogenated rosin
  • examples of the rosin ester generally include esters of natural rosin, modified rosin, and/or hydrogenated rosin.
  • the rosin ester may be, for example, a glycerol ester of natural rosin, a glycerol ester of modified rosin, a glycerol ester of hydrogenated rosin, a pentaerythritol ester of natural rosin, a pentaerythritol ester of modified rosin, or a pentaerythritol ester of hydrogenated rosin.
  • rosin ester a commercially available product can be used.
  • examples thereof include: KOMOTAC KB90H (trade name), KOMOTAC KH100 (trade name), KOMOTAC KHR75 (trade name), and KOMOTAC K107 (trade name), which are manufactured by Guangdong Komo Co., Ltd.; FORALYN 5020-F (trade name), FORAL AX-E (trade name), and FORAL 85E (trade name), which are manufactured by Eastman Chemical Company Japan; and SYLVALITE 9100 (trade name) manufactured by Kraton Corporation.
  • the adhesive for laminates according to one embodiment of the present invention may contain the (D) tackifier resin in an amount of 0 to 60 parts by mass, preferably 5 to 50 parts by mass, more preferably 10 to 40 parts by mass, per 100 parts by mass of the total mass of the components (A) and (B).
  • the adhesive for laminates according to one embodiment of the present invention has a superior adhesive strength and can further improve the appearance of films.
  • the adhesive for laminates according to one embodiment of the present invention may contain other components such as various additives, in addition to the components (A) to (D).
  • the other components are not particularly limited as long as they are components that are generally contained in an adhesive for laminates and the adhesive for laminates according to one embodiment of the present invention can be obtained.
  • examples of such other components include a solvent, a pigment, a plasticizer (excluding the above-described components (C) and (D)), a catalyst, and an adhesion promoter.
  • pigment examples include nanopigments based on TiO 2 , SiO 2 , Fe 2 O 3 , a similar oxide, or an oxyhydrate. These pigments usually have a particle size of preferably 500 nm or smaller, more preferably smaller than 100 nm.
  • plasticizer examples include castor oil-based compounds, white oils, naphthenic mineral oils, paraffin hydrocarbon oils, polypropylene oligomers, polybutene oligomers, polyisoprene oligomers, hydrogenated polyisoprenes and/or polybutadiene oligomers, phthalates, adipates, benzoate esters, vegetable oils, animal oils, and derivatives thereof.
  • Vegetable oils, animal oils, and derivatives thereof are generally used in food products and thus believed to be safer; therefore, they are more preferred taking into consideration the use of the adhesive for laminates according to one embodiment of the present invention in the production of food packaging films.
  • Catalyst examples include: metal catalysts, such as tin catalysts (e.g., trimethyltin laurate, trimethyltin hydroxide, dibutyltin dilaurate, and dibutyltin maleate), lead-based catalysts (e.g., lead oleate, lead naphthenate, and lead octoate), and other metal catalysts (e.g., metal naphthenates such as cobalt naphthenate); and amine-based catalysts, such as triethylenediamine, tetramethylethylenediamine, tetramethylhexylenediamine, diazabicycloalkenes, and dialkylaminoalkylamines.
  • metal catalysts such as tin catalysts (e.g., trimethyltin laurate, trimethyltin hydroxide, dibutyltin dilaurate, and dibutyltin maleate)
  • lead-based catalysts e.g., lead
  • adhesion promoter examples include silane compounds.
  • any known organic functional silane such as a (meth)acryloxy functional silane, an epoxy functional silane, an amine functional silane, or a non-reactive substituted silane can be used.
  • Examples thereof include vinyltrialkoxysilanes, alkyltrialkoxysilanes, tetraalkoxysilanes, 3-acryloxypropyltrialkoxysilanes, 3-methacryloxypropyltrialkoxysilanes, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-glycidyloxymethyltrimethoxysilane, 3-glycidyloxymethyltriethoxysilane, and 2-glycidyloxyethyltrimethoxysilane.
  • the adhesive for laminates preferably contains an adhesion promoter in an amount of 0.1 to 5 parts by mass per 100 parts by mass (solid content) of the total mass of the adhesive.
  • the adhesive for laminates according to one embodiment of the present invention can be produced by mixing the components (A) and (B) and, if necessary, the component (C) and/or the component (D).
  • the adhesive for laminates according to one embodiment of the present invention may be a two-part liquid adhesive (two-pack type adhesive or two-component type adhesive)for laminates which contains (or is obtained from) a first liquid containing the component (A) and a second liquid containing the component (B).
  • the adhesive for laminates according to one embodiment of the present invention may be a two-part liquid adhesive for laminates which is obtained by blending a first liquid containing the component (A) with a second liquid containing the components (B) to (D) and contains these two liquids, or may be a two-part liquid adhesive for laminates which is obtained by blending a first liquid containing the components (A), (C), and (D) with a second liquid containing the component (B) and contains these two liquids.
  • the first liquid and the second liquid may each contain other components as appropriate.
  • the adhesive for laminates according to one embodiment of the present invention is more preferably a two-part liquid adhesive for laminates which is obtained by blending a first liquid containing the component (A) with a second liquid containing the components (B) to (D) and contains these two liquids.
  • a mixing method is not particularly limited as long as the adhesive for laminates that is intended by the present invention can be obtained.
  • the order and the like of mixing the components are also not particularly limited.
  • the adhesive for laminates according to one embodiment of the present invention can be produced without requiring a special mixing method, a special mixing order, and the like.
  • the resulting adhesive for laminates exhibits a small reduction in the adhesive strength to a film as well as in the adhesive strength over time.
  • the adhesive for laminates according to one embodiment of the present invention is usually applied to a film at 15 to 100°C and, therefore, should have a low viscosity in this temperature range.
  • the viscosity (measured by a Brookfield viscometer) of an adhesive for food packaging films is preferably 300 to 5,000 mPa.s at 40°C and 200 to 4,000 mPa.s at 50°C.
  • the viscosity of the adhesive for laminates according to one embodiment of the present invention is in this range, since the adhesive for laminates can be applied to films more uniformly, the adhesive strength and the film appearance can be further improved.
  • the laminated film according to one embodiment of the present invention is a laminate produced using the above-described adhesive for laminates.
  • Films to be used for the formation of the laminate are not particularly limited as long as the laminate according to one embodiment of the present invention can be obtained, and examples of the films include films having a metal layer formed on a plastic substrate, and films without a metal layer formed thereon.
  • the adhesive for laminates according to one embodiment of the present invention is applied to the films.
  • the application can be performed by various methods, such as gravure coating, wire bar coating, air knife coating, die coating, lip coating, and comma coating.
  • a laminated film can be produced by bonding together a plurality of films using the adhesive for laminates according to one embodiment of the present invention.
  • the adhesive for laminates is applied to the films, the applied amount is preferably 0.5 to 10 g/m 2 , more preferably 1 to 5 g/m 2 .
  • the laminated film according to one embodiment of the present invention is a laminate obtained by bonding together a plurality of films using the above-described adhesive.
  • FIGs. 1 and 2 each illustrate an example of one embodiment of the present invention; however, the present invention is not limited thereto.
  • FIG. 1 schematically illustrates a cross-section of a laminated film according to one embodiment of the present invention.
  • a laminated film 10 is formed of two films and an adhesive 13 for laminated films that is interposed between the two films, and the two films 11 and 12 are bonded together by the adhesive 13 for laminated films.
  • the films 11 and 12 may be made of the same material or different materials.
  • the two films 11 and 12 are bonded with each other; however, three or more films may be bonded together as well.
  • FIG. 2 schematically illustrates a cross-section of a laminated film according to another embodiment of the present invention.
  • a thin film 11a is formed between the film 11 and the adhesive 13 for laminated films.
  • FIG. 2 represents an embodiment in which a metal thin film 11a is formed on the surface of the film 11.
  • the metal thin film 11a can be formed by, for example, vapor deposition on the surface of the plastic film 11, and the laminated film according to FIG. 2 can be obtained by bonding the film 11, on which the metal thin film 11a is formed, with the film 12 through the adhesive 13 for laminated films.
  • the metal to be vapor-deposited on the plastic film examples include aluminum, steel, and copper. By performing vapor deposition on the plastic film, the film can be imparted with a barrier property.
  • a vapor deposition material for example, silicon oxide or aluminum oxide is used.
  • the plastic film 11 used as a substrate may be transparent or colored in white, black, or the like.
  • a plastic film formed of a polyvinyl chloride, a polyester, a fluororesin, an acrylic resin, or the like may be used and, for the purpose of imparting heat resistance, weather resistance, rigidity, insulating property and the like, it is particularly preferred to use, for example, a polyethylene terephthalate film or a polybutylene terephthalate film.
  • the films 11 and 12 may be transparent or colored.
  • the vapor-deposited thin film 11a of the film 11 and the film 12 are bonded together using the adhesive 13 for laminated films according to one embodiment of the present invention; and, the films 11 and 12 are often laminated by a dry lamination method. Accordingly, the adhesive 13 for laminated films is required to be excellent in initial adherence to the films at the time of the lamination, as well as in adhesion to the films after curing.
  • the laminated film according to one embodiment of the present invention is used for the production of various packaging bags and outdoor materials.
  • the packaging bags refer to bag-like articles that are obtained by processing a laminated film for enclosure of a food item, a detergent, a shampoo, a conditioner, or the like therein.
  • outdoor materials include articles that are used outdoors, such as protective wall materials, roofing materials, solar cell modules, window materials, outdoor flooring materials, illumination protective materials, automobile members, and signboards.
  • These packaging bags and outdoor materials take a form that includes a laminated film obtained by bonding a plurality of films together.
  • C Polyether Polyol
  • C1 SANNIX PP400 (bifunctional polypropylene glycol, Mn: 400, hydroxyl value: 365 mgKOH/g, manufactured by Sanyo Chemical Industries, Ltd.)
  • C2) EXCENOL 1020 (bifunctional polypropylene glycol, Mn: 1,000, hydroxyl value: 111 mgKOH/g, manufactured by AGC Inc.)
  • C3) SANNIX GP1500 trifunctional polyoxypropylene glyceryl ether, Mn: 1,500, hydroxyl value: 111 mgKOH/g, manufactured by Sanyo Chemical Industries, Ltd.)
  • D Tackifier Resin (D1) QUINTONE 1500 (alicyclic petroleum resin, softening point: 100°C, manufactured by Zeon Corporation)
  • D2 KOMOTAC KB90H (rosin ester, softening point: 90°C, acid value: 0 to 10 mgKOH/g, manufactured by Guangdong Komo Co., Ltd.)
  • D3 SYLVALITE 9100 (rosin ester, softening point: 105°C, acid value: 7 mgKOH/g, manufactured by Kraton Corporation)
  • the components (A) to (E) were mixed as shown in Table 2 to produce adhesives for laminates of Examples 1 to 6 and Comparative Examples 1 to 3. Specifically, the components (B) to (E) were mixed in accordance with the respective formulations (parts by mass) shown in Table 2, followed by 1-hour stirring at 120°C. The resulting mixtures were allowed to cool, and the component (A) was subsequently added thereto. The added amount of the component (A) is the number of parts shown in Table 2. Thereafter, the mixtures of the components (A) to (E) were each stirred at 40°C for 5 minutes to prepare adhesives for laminates.
  • the adhesives for laminates of Examples were each applied to the side of a solid-white printed surface of a PET film such that the applied adhesive had a solid mass of 2 g/m 2 .
  • the films were press-bonded such that voids between the adhesive and the vapor-deposited surface were removed as much as possible. Thereafter, the resultant was cured for 24 hours in a 40°C atmosphere to obtain a laminated film.
  • the initial viscosity of each adhesive for laminates was measured using a Brookfield viscometer in accordance with the method B of JAI 7-1991. Specifically, the viscosity at 40°C was measured using a No. 27 rotor at a rotation speed of 1 rpm.
  • the above-described apparatus was set up immediately after the preparation of the adhesive for laminates, and the viscosity at 1 minute after the start of the measurement (start of rotor rotation) was defined as the initial viscosity (also referred to as " ⁇ 1").
  • the above-obtained laminated films after 24-hour curing were each cut at a width of 15 mm in the TD direction and subjected to a peeling test using a tensile strength tester (TENSILON RTM-250 (trade name), manufactured by Orientec Co., Ltd.) to measure the adhesive strength.
  • the peeling test was conducted at a tensile speed of 300 mm/min under the T-type peeling condition after each laminated film was left to stand for at least 24 hours in a room-temperature environment (23°C).
  • the evaluation criteria were as follows. ⁇ : The adhesive strength was 1.0 N/15 mm or more.
  • the adhesive strength was 0.75 N/15 mm or more but less than 1.0 N/15 mm ⁇ : The adhesive strength was 0.5 N/15 mm or more but less than 0.75 N/15 mm ⁇ : The adhesive strength was less than 0.5 N/15 mm. -: It was difficult to measure the adhesive strength due to poor compatibility.
  • the adhesives for laminates of Examples 1 to 6 not only were excellent in the compatibility of the components (A) and (E) and imparted films with an extremely high level of appearance, but also were excellent in adhesion to a film having a printed part and exhibited an excellent balance of performance.
  • the adhesive for laminates according to one embodiment of the present invention can be sufficiently utilized as, for example, an adhesive for laminates such as food packaging bags that are required to have an extremely high level of appearance.
  • the adhesives for laminates of Comparative Examples 1 to 3 did not contain any phenol-based compound derived from a cashew nut shell liquid and thus could not improve the film appearance.
  • the adhesive for laminates according to one embodiment of the present invention is excellent in compatibility, exhibits an excellent adhesive strength without degrading the appearance of films, and has an excellent balance of performance.
  • the adhesive for laminates according to one embodiment of the present invention can be utilized in various applications since, when bonding a plurality of films together, the adhesive not only exhibits an excellent adhesive strength after curing without degrading the appearance of the films, but also is excellent in uniformity and inhibition of turbidity and has an excellent balance of performance.
  • the adhesive for laminates according to one embodiment of the present invention is suitable as an adhesive for a laminated film used for packaging a food item, a detergent, a shampoo, a conditioner, or the like.

Abstract

Disclosed is an adhesive for laminates, comprising: (A) a urethane prepolymer having an isocyanate group at the end; and (B) a phenol-based compound derived from a cashew nut shell liquid.

Description

ADHESIVE FOR LAMINATES
The present invention relates to an adhesive for laminates. More particularly, the present invention relates to: an adhesive for laminates, which is excellent in stability and adhesion and does not degrade the appearance of films when bonding a plurality of films together; and a laminated film using the same.
Plastic films (e.g., films made of polyethylene, polypropylene, nylon, polyester, polyimide, or the like), metal vapor-deposited films, and composite films obtained by bonding together metal foils (e.g., foils made of aluminum, copper, or the like) are used in the production of packaging materials of food products, medical products, cosmetic products and the like, as well as substrates such as FPC substrates and TAB substrates. As adhesives for bonding these plastic films, metal vapor-deposited films, metal foils and the like, urethane adhesives containing a combination of an organic polyol and an organic isocyanate are known.
Recently, in consideration of the environment, simple equipment, cost benefit and the like, there is an increasing demand for solvent-free adhesives as urethane adhesives. As compared to solvent-based adhesives, the solvent-free adhesives are advantageous in that they do not use any solvent; however, they are poor in wettability and are likely to cause generation of voids on the film surfaces at the time of bonding a plurality of films together, which may degrade the appearance of the films. Particularly, defective appearance often occurs in polyethylene terephthalate films on which aluminum is vapor-deposited.
PTLs 1 to 3 disclose laminated films that are laminated using an urethane adhesive.
PTL 1 discloses: a urethane adhesive composition obtained by mixing a polyisocyanate and a polyol with an ester that is liquid at 25°C; and a laminate obtained by applying the composition (see [Claims] and [Table 1] to [Table 6] of PTL 1).
PTL 2 discloses a solvent-free laminate adhesive that contains a polyisocyanate, a polyol, and castor oil (or a castor oil derivative) (see [Claims], [Table 1], and [Table 2] of PTL 2).
PTL 3 discloses a one-part liquid adhesive (one-pack type adhesive or one-component type adhesive) that contains a polyester-based urethane resin, a specific polyol, and a polyisocyanate (see [Claims] of PTL 3). Table 4 of PTL 3 discloses adhesives that contain a polyester-based urethane resin, a rosin ester, and diphenylmethane diisocyanate (see [Claim 4] and [Table 4] of PTL 3).
PTLs 1 to 3 describe that the respective adhesives improve the appearance of a laminated film (see PTL 1 [0017], PTL 2 [0015], and PTL 3 [0005]); however, they cannot be said to sufficiently satisfy the high demand of consumers. Further, in consideration of the working efficiency in the production of a packaging bag using the laminated film, the adhesive is desired to have an excellent compatibility of its components as well as an excellent adhesive strength to films after curing.
[PTL 1] JP 2018-162420 A
[PTL 2] WO 2016/152370
[PTL 3] JP H08-048962 A
The present invention was conceived to solve the above-described problems, and an object of the present invention is to provide: an adhesive for laminates which, in the production of a laminated film by laminating plastic films, exhibits an excellent adhesive strength to the films after curing and an excellent compatibility of components, allows efficient coating process and film production without degrading the appearance of the laminated film, and has an excellent balance of these properties; and a laminated film produced using the adhesive for laminates, which laminated film has an excellent appearance and an excellent balance of the above-described properties.
The present inventor intensively studied to solve the above-described problems and consequently discovered that a urethane resin composition which contains a urethane prepolymer, a polyether polyol, and a specific phenol-based compound not only is excellent in compatibility of components and has an excellent adhesive strength to films in the production of a laminated film by lamination of plastic films, but also exhibits an excellent balance of these properties without degrading the appearance of the resulting laminated film, thereby completing the present invention.
The present specification encompasses the following embodiments.
1. An adhesive for laminates, comprising:
(A) a urethane prepolymer having an isocyanate group at the end; and
(B) a phenol-based compound derived from a cashew nut shell liquid (CNSL).
2. The adhesive for laminates according to 1, wherein the (B) phenol-based compound comprises a cardanol derivative.
3. The adhesive for laminates according to 1 or 2, wherein the adhesive comprises the component (B) in an amount of 5 to 70 parts by mass per 100 parts by mass of the total mass of the components (A) and (B).
4. The adhesive for laminates according to any one of 1 to 3, further comprising (C) a polyether polyol.
5. The adhesive for laminates according to 4, wherein the (C) polyether polyol comprises a polypropylene glycol having a number average molecular weight of 300 to 2,000.
6. The adhesive for laminates according to any one of claims 1 to 5, further comprising (D) a tackifier resin.
7. The adhesive for laminates according to 6, wherein the (D) tackifier resin comprises a natural resin having a softening point of 80 to 120°C.
8. The adhesive for laminates according to 7, wherein the natural resin comprises a rosin ester.
9. A laminated film in which a plurality of films are bonded through the adhesive for laminates according to any one of 1 to 8.
The adhesive for laminates according to one embodiment of the present invention contains (A) a urethane prepolymer having an isocyanate group at the end and (B) a phenol-based compound derived from a cashew nut shell liquid (CNSL); therefore, the adhesive for laminates is excellent in compatibility and adhesive strength, and has an excellent balance of these properties. When a laminated film is produced by laminating plastic films using the adhesive for laminates according to one embodiment of the present invention, the appearance of the laminated film is not degraded.
The laminated film according to one embodiment of the present invention is obtained using the above-described adhesive for laminates; therefore, lamination can be performed quickly, and the laminated film has an excellent appearance as well as an excellent balance of these properties and is produced in an efficient manner.
FIG. 1 schematically illustrates a cross-section of a laminated film according to one embodiment of the present invention. FIG. 2 schematically illustrates a cross-section of a laminated film according to another embodiment of the present invention.
The adhesive for laminates according to one embodiment of the present invention contains (A) a urethane prepolymer having an isocyanate group at the end (hereinafter, also referred to as "component (A)") and (B) a phenol-based compound derived from a cashew nut shell liquid (CNSL) (hereinafter, also referred to as "component (B)"). As required, (C) a polyether polyol (hereinafter, also referred to as "component (C)") and/or (D) a tackifier resin (hereinafter, also referred to as "component (D)") may be blended (or mixed) therein. Accordingly, the adhesive for laminates according to one embodiment of the present invention contains the component (A) and the component (B), and may contain at least one selected from the component (C) and the component (D).
The adhesive according to one embodiment of the present invention is not particularly limited in terms of the order, the method, and the like of blending the components (A) to (D) (the components (A) and (B), and the components (C) and (D) that may be blended) as long as an intended adhesive can be obtained. The adhesive according to one embodiment of the present invention can be obtained by, for example, simultaneously blending the (A) urethane prepolymer, the (B) phenol-based compound derived from a cashew nut shell liquid, the (C) polyether polyol, and the (D) tackifier resin; however, the adhesive according to one embodiment of the present invention is more preferably obtained by mixing the components (B) and (C) in advance and subsequently blending the resulting mixture with the component (A).
The production of the adhesive by blending (or mixing) of the components (A) to (D) can be carried out by any known method. The adhesive can be obtained by blending the components (A) to (D) in a solvent, or the components (A) to (D) can be blended with each other without using a solvent.
The adhesive according to one embodiment of the present invention may be a two-part liquid adhesive, and this two-part liquid adhesive may be one obtained from a first liquid containing the component (A) and a second liquid containing the component (B), one obtained by blending a first liquid containing the component (A) with a second liquid containing the components (B), (C), and (D), or one obtained by blending a first liquid containing the components (A) and (D) with a second liquid containing the components (B) and (C).
The adhesive according to one embodiment of the present invention is more preferably a two-part liquid adhesive that contains a first liquid containing the component (A) and a second liquid containing the components (B), (C), and (D). The first liquid and the second liquid may each further contain the below-described various additives and the like as appropriate.
<(A) Urethane Prepolymer Having Isocyanate Group at End>
In one embodiment of the present invention, the (A) urethane prepolymer is a product of a reaction between (a1) a polyol and (a2) an isocyanate monomer. The number average molecular weight of the (A) urethane prepolymer may be, for example, 400 to 20,000, and it is preferably 1,000 to 10,000, particularly preferably 1,500 to 4,000. When the number average molecular weight of the (A) urethane prepolymer is in this range, the adhesive for laminates according to one embodiment of the present invention exhibits superior adhesion.
In the present specification, the number average molecular weight (Mn) is a value that is measured by gel permeation chromatography (GPC) and converted using a polystyrene standard. Specifically, this value can be measured using the following GPC apparatus and measurement method and then converted. HCL-8220GPC manufactured by Tosoh Corporation is used as a GPC apparatus, and RI is used as a detector. As GPC columns, two TSKgel SuperMultipore HZM columns manufactured by Tosoh Corporation are used. A sample is dissolved in tetrahydrofuran, and the resulting solution is applied to the columns at a flow rate of 0.35 ml/min and a column temperature of 40°C to obtain a measurement value. This measurement value is converted based on a calibration curve prepared using a polystyrene having a monodisperse molecular weight as a standard substance, whereby the objective Mn is determined. The same also applies to the Mn of the below-described (a1) polyol and the Mn of the below-described (a2) isocyanate monomer.
In the present specification, "(a1) polyol" is a general term for a compound having two or more hydroxy groups in one molecule, and examples thereof include polyether polyols, polyester polyols, acrylic polyols, polycaprolactone polyols, and polycarbonate polyols. The type of the (a1) polyol is not limited as long as the adhesive according to one embodiment of the present invention can be obtained.
In one embodiment of the present invention, the number average molecular weight of the (a1) "polyol" may be, for example, 100 to 4,000, and it is preferably 400 to 2,000. When the number average molecular weight is in this range, the (a1) polyol has a short chain length and is thus likely to crosslink with the (a2) isocyanate monomer. This leads to a further reduction in the amount of unreacted (a2) isocyanate monomer; therefore, the adhesive for laminates according to one embodiment of the present invention contains a greater amount of the (A) urethane prepolymer and exhibits superior adhesion.
In one embodiment of the present invention, the (a2) isocyanate monomer is not particularly limited as long as the adhesive for laminates that is intended by the present invention can be obtained; however, the (a2) isocyanate monomer preferably contains an aromatic isocyanate. When the (a2) isocyanate monomer contains an aromatic isocyanate, the adhesion of the adhesive for laminates according to one embodiment of the present invention is further improved.
In one embodiment of the present invention, the "(a2) isocyanate monomer" is not meant to consist of an aromatic isocyanate. The (a2) isocyanate monomer may also contain an aliphatic isocyanate and/or an alicyclic isocyanate within a range that does not adversely affect the adhesion of the adhesive for laminates according to one embodiment of the present invention and the appearance of a film.
The term "aliphatic isocyanate" used herein refers to a compound having a chain-like hydrocarbon chain to which an isocyanate group is directly bound, and the compound does not have a cyclic hydrocarbon chain. The "aliphatic isocyanate" may have an aromatic ring; however, the aromatic ring and the isocyanate group are not directly bound to each other.
It is noted here that, in the present specification, an aromatic ring is not included in the cyclic hydrocarbon chain.
The term "alicyclic isocyanate" used herein refers to a compound which has a cyclic hydrocarbon chain and optionally has a chain-like hydrocarbon chain. An isocyanate group may be directly bound to the cyclic hydrocarbon chain, or may be directly bound to the optional chain-like hydrocarbon chain. The "alicyclic isocyanate" may have an aromatic ring; however, the aromatic ring and the isocyanate group are not directly bound to each other.
The term "aromatic isocyanate" used herein refers to a compound having an aromatic ring to which an isocyanate group is directly bound. Accordingly, a compound in which an isocyanate group is not directly bound to an aromatic ring is classified as either an aliphatic isocyanate or an alicyclic isocyanate, even if the compound has an aromatic ring in its molecule.
Therefore, for example, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate (OCN-C6H4-CH2-C6H4-NCO) correspond to aromatic isocyanates since isocyanate groups are each directly bound to an aromatic ring in these compounds.
Meanwhile, for example, xylylene diisocyanate (OCN-CH2-C6H4-CH2-NCO) corresponds to an aliphatic isocyanate since it has an aromatic ring but isocyanate groups are not directly bound to the aromatic ring and are each bound to a methylene group.
The aromatic ring may be a fused ring of two or more benzene rings.
Examples of the aromatic isocyanate include 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate.
Examples of the aliphatic isocyanate include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (hereinafter also referred to as "HDI"), 1,6-diisocyanato-2,2,4-trimethylhexane, methyl 2,6-diisocyanatohexanoate (lysine diisocyanate), and 1,3-bis(isocyanatomethyl)benzene (xylylene diisocyanate).
Examples of the alicyclic isocyanate include 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane (isophorone diisocyanate: IPDI), 1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated xylylene diisocyanate), bis(4-isocyanatocyclohexyl)methane (hydrogenated diphenylmethane diisocyanate), and 1,4-diisocyanatocyclohexane.
In one embodiment of the present invention, a method of performing the reaction between the (a1) polyol and the (a2) isocyanate monomer is not limited as long as the (A) urethane prepolymer according to one embodiment of the present invention can be obtained, and any general urethanization method may be employed. For example, bulk polymerization using no solvent and solution polymerization using a solvent can be employed. The resultant is heated and stirred as appropriate, and a catalyst may be used as required. Further, there is no problem in using various additives during the reaction between the (a1) polyol and the (a2) isocyanate monomer.
Examples of a commercially available product of the (A) urethane prepolymer include LOCTITE LIOFOL LA Series manufactured by Henkel Japan Ltd.
<(B) Phenol-Based Compound Derived from Cashew Nut Shell Liquid (CNSL)>
The adhesive for laminates according to one embodiment of the present invention contains (B) a phenol-based compound derived from a cashew nut shell liquid. Such phenol-based compounds may be used singly, or in combination. By incorporating the (B) phenol-based compound derived from a cashew nut shell liquid, the appearance of films can be improved when the films are bonded together.
In the present specification, since the (B) phenol-based compound reacts with the isocyanate group contained in the component (A), the component (A) hardly reacts with the moisture in the air. In the adhesive for laminates according to one embodiment of the present invention, the component (A) is likely to react with the component (B) at the time of bonding films together, so that voids are unlikely to be formed between the films.
The "cashew nut shell liquid" refers to a liquid that contains a phenol-based compound collected from shells encapsulating cashew nuts. Examples of the phenol-based compound include anacardic acid, cardanol, cardol, and 2-methylcardol. The chemical structures of these compounds are shown below.
Figure JPOXMLDOC01-appb-I000001
In the above structural formulae, R is a hydrocarbon group represented by C15Hn (wherein, n represents an integer of 19 to 31), and n is preferably an integer of 25 to 31.
In the case of cardanol, for example, R may be C15H25, C15H27, C15H29, C15H31, or a combination thereof. In the case of cardanol, when n is an integer of 25 to 31, R may be, for example, the following mixture.
Figure JPOXMLDOC01-appb-I000002
As shown in Table 1 below, a natural CNSL contains anacardic acid as a main component. This CNSL is heated when industrially utilized, and anacardic acid is decarboxylated into cardanol. Therefore, an industrial CNSL contains cardanol as a main component.
Figure JPOXMLDOC01-appb-T000003
The adhesive for laminates according to one embodiment of the present invention preferably contains a cardanol derivative as the (B) phenol-based compound derived from a cashew nut shell liquid. The term "cardanol derivative" used herein refers to a compound having a chemical structure derived from cardanol, and specific examples thereof include a cardanol monomer, a cardanol polymer (polymer based on a cardanol monomer), and a cardanol modification product (a modification product obtained by partial substitution of the chemical structure of cardanol with other functional group).
The adhesive for laminates according to one embodiment of the present invention, when it contains a cardanol derivative, can further improve the appearance of films that are bonded together.
A commercially available product can be used as the cardanol derivative. Examples of a commercially available product of a cardanol polymer include NX9201LP (CNSL polyester, manufactured by Cardolite Japan Ltd.), NX9001LV (CNSL novolac, manufactured by Cardolite Japan Ltd.), and NX9016 (CNSL novolac, manufactured by Cardolite Japan Ltd.).
The adhesive for laminates according to one embodiment of the present invention contains the component (B) in an amount of preferably 5 to 70 parts by mass, more preferably 5 to 60 parts by mass, most preferably 10 to 60 parts by mass, per 100 parts by mass of the total mass of the components (A) and (B).
When the adhesive for laminates according to one embodiment of the present invention contains the component (B) at the above-described ratio, the adhesive can have an improved compatibility of components and an improved adhesive strength while further reducing the amount of voids generated at the time bonding films together and thereby improving the appearance of the films.
<(C) Polyether Polyol>
The adhesive for laminates according to one embodiment of the present invention may further contain (C) a polyether polyol. In the present specification, the "(C) polyether polyol" usually refers to a compound understood as a polyether polyol, and is not particularly limited as long as the adhesive for laminates that is intended by the present invention can be obtained. Examples of the (C) polyether polyol include polyethylene glycols (PEG), polyoxytetramethylene glycols (PTMG), and polypropylene glycols (PPG). The (C) polyether polyol can be used singly, or in combination.
Generally, the (C) polyether polyol is produced by, for example, addition polymerization of an alkylene oxide, such as propylene oxide or ethylene oxide, with a low-molecular-weight compound having two or more hydroxy groups in the molecule, such as propylene glycol, glycerin, sorbitol or sucrose, and/or a polyamine.
In the adhesive for laminates according to one embodiment of the present invention, an increase in viscosity is inhibited and superior compatibility of components is obtained by incorporating the (C) polyether polyol, and this contributes to an improvement in the adhesive strength.
In the adhesive for laminates according to one embodiment of the present invention, the (C) polyether polyol preferably contains a polypropylene glycol having a number average molecular weight of 300 to 2,000. When the component (C) contains a polypropylene glycol having a number average molecular weight of 300 to 2,000, the adhesive for laminates according to one embodiment of the present invention not only has excellent compatibility of components and is more suitable for a film coating process in the production of a laminated film, but also has a further improved adhesive strength.
The adhesive for laminates according to one embodiment of the present invention may contain the (C) polyether polyol in an amount of 0 to 50 parts by mass, preferably 5 to 40 parts by mass, more preferably 5 to 30 parts by mass, per 100 parts by mass of the total mass of the components (A) and (B).
When the content of the (C) polyether polyol is in this range, the adhesive for laminates according to one embodiment of the present invention can have superior compatibility and adhesive strength.
<(D) Tackifier Resin>
As a preferred embodiment of the present invention, the adhesive for laminates preferably contains (D) a tackifier resin. By containing the (D) tackifier resin, the adhesive for laminates according to this embodiment of the present invention exhibits a superior adhesive strength and further improves the appearance of films at the time of bonding the films together.
Examples of the (D) tackifier resin include styrene-based resins, terpene-based resins, aliphatic petroleum resins, aromatic petroleum resins, rosin esters, acrylic resins, and polyester resins (excluding polyester polyols), and the (D) tackifier resin preferably has a softening point of 80 to 120°C.
When the softening point of the (D) tackifier resin is in this range, the adhesive for laminates according to one embodiment of the present invention not only can maintain a more appropriate hardness and has a superior adhesive strength, but also can further inhibit the generation of voids and thereby further improve the appearance of films when applied to the films.
As the tackifier resin, a commercially available product can be used.
The (D) tackifier resin preferably contains a rosin ester. When the adhesive for laminates according to one embodiment of the present invention contains a rosin ester, the compatibility of components is further improved, so that the adhesive strength is further improved.
Examples of rosin generally include natural rosin, modified rosin, and hydrogenated rosin, and examples of the rosin ester generally include esters of natural rosin, modified rosin, and/or hydrogenated rosin. The rosin ester may be, for example, a glycerol ester of natural rosin, a glycerol ester of modified rosin, a glycerol ester of hydrogenated rosin, a pentaerythritol ester of natural rosin, a pentaerythritol ester of modified rosin, or a pentaerythritol ester of hydrogenated rosin.
As the rosin ester, a commercially available product can be used. Examples thereof include: KOMOTAC KB90H (trade name), KOMOTAC KH100 (trade name), KOMOTAC KHR75 (trade name), and KOMOTAC K107 (trade name), which are manufactured by Guangdong Komo Co., Ltd.; FORALYN 5020-F (trade name), FORAL AX-E (trade name), and FORAL 85E (trade name), which are manufactured by Eastman Chemical Company Japan; and SYLVALITE 9100 (trade name) manufactured by Kraton Corporation.
The adhesive for laminates according to one embodiment of the present invention may contain the (D) tackifier resin in an amount of 0 to 60 parts by mass, preferably 5 to 50 parts by mass, more preferably 10 to 40 parts by mass, per 100 parts by mass of the total mass of the components (A) and (B).
When the content of the (D) tackifier resin is in this range, the adhesive for laminates according to one embodiment of the present invention has a superior adhesive strength and can further improve the appearance of films.
As required, the adhesive for laminates according to one embodiment of the present invention may contain other components such as various additives, in addition to the components (A) to (D). The other components are not particularly limited as long as they are components that are generally contained in an adhesive for laminates and the adhesive for laminates according to one embodiment of the present invention can be obtained. Examples of such other components include a solvent, a pigment, a plasticizer (excluding the above-described components (C) and (D)), a catalyst, and an adhesion promoter.
Examples of the "pigment" include nanopigments based on TiO2, SiO2, Fe2O3, a similar oxide, or an oxyhydrate. These pigments usually have a particle size of preferably 500 nm or smaller, more preferably smaller than 100 nm.
Examples of the "plasticizer" include castor oil-based compounds, white oils, naphthenic mineral oils, paraffin hydrocarbon oils, polypropylene oligomers, polybutene oligomers, polyisoprene oligomers, hydrogenated polyisoprenes and/or polybutadiene oligomers, phthalates, adipates, benzoate esters, vegetable oils, animal oils, and derivatives thereof.
Vegetable oils, animal oils, and derivatives thereof are generally used in food products and thus believed to be safer; therefore, they are more preferred taking into consideration the use of the adhesive for laminates according to one embodiment of the present invention in the production of food packaging films.
Examples of the "catalyst" include: metal catalysts, such as tin catalysts (e.g., trimethyltin laurate, trimethyltin hydroxide, dibutyltin dilaurate, and dibutyltin maleate), lead-based catalysts (e.g., lead oleate, lead naphthenate, and lead octoate), and other metal catalysts (e.g., metal naphthenates such as cobalt naphthenate); and amine-based catalysts, such as triethylenediamine, tetramethylethylenediamine, tetramethylhexylenediamine, diazabicycloalkenes, and dialkylaminoalkylamines.
Examples of the "adhesion promoter" include silane compounds. As the adhesion promoter, any known organic functional silane such as a (meth)acryloxy functional silane, an epoxy functional silane, an amine functional silane, or a non-reactive substituted silane can be used. Examples thereof include vinyltrialkoxysilanes, alkyltrialkoxysilanes, tetraalkoxysilanes, 3-acryloxypropyltrialkoxysilanes, 3-methacryloxypropyltrialkoxysilanes, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-glycidyloxymethyltrimethoxysilane, 3-glycidyloxymethyltriethoxysilane, and 2-glycidyloxyethyltrimethoxysilane.
In one embodiment of the present invention, the adhesive for laminates preferably contains an adhesion promoter in an amount of 0.1 to 5 parts by mass per 100 parts by mass (solid content) of the total mass of the adhesive.
As described above, the adhesive for laminates according to one embodiment of the present invention can be produced by mixing the components (A) and (B) and, if necessary, the component (C) and/or the component (D). The adhesive for laminates according to one embodiment of the present invention may be a two-part liquid adhesive (two-pack type adhesive or two-component type adhesive)for laminates which contains (or is obtained from) a first liquid containing the component (A) and a second liquid containing the component (B). Alternatively, the adhesive for laminates according to one embodiment of the present invention may be a two-part liquid adhesive for laminates which is obtained by blending a first liquid containing the component (A) with a second liquid containing the components (B) to (D) and contains these two liquids, or may be a two-part liquid adhesive for laminates which is obtained by blending a first liquid containing the components (A), (C), and (D) with a second liquid containing the component (B) and contains these two liquids.
Depending on the case, other components may be mixed as well. The first liquid and the second liquid may each contain other components as appropriate.
The adhesive for laminates according to one embodiment of the present invention is more preferably a two-part liquid adhesive for laminates which is obtained by blending a first liquid containing the component (A) with a second liquid containing the components (B) to (D) and contains these two liquids.
A mixing method is not particularly limited as long as the adhesive for laminates that is intended by the present invention can be obtained. The order and the like of mixing the components are also not particularly limited. The adhesive for laminates according to one embodiment of the present invention can be produced without requiring a special mixing method, a special mixing order, and the like. The resulting adhesive for laminates exhibits a small reduction in the adhesive strength to a film as well as in the adhesive strength over time.
The adhesive for laminates according to one embodiment of the present invention is usually applied to a film at 15 to 100°C and, therefore, should have a low viscosity in this temperature range. Taking into consideration the applicability, the viscosity (measured by a Brookfield viscometer) of an adhesive for food packaging films is preferably 300 to 5,000 mPa.s at 40°C and 200 to 4,000 mPa.s at 50°C.
When the viscosity of the adhesive for laminates according to one embodiment of the present invention is in this range, since the adhesive for laminates can be applied to films more uniformly, the adhesive strength and the film appearance can be further improved.
The laminated film according to one embodiment of the present invention is a laminate produced using the above-described adhesive for laminates. Films to be used for the formation of the laminate are not particularly limited as long as the laminate according to one embodiment of the present invention can be obtained, and examples of the films include films having a metal layer formed on a plastic substrate, and films without a metal layer formed thereon.
For the production of a laminated film, the adhesive for laminates according to one embodiment of the present invention is applied to the films. The application can be performed by various methods, such as gravure coating, wire bar coating, air knife coating, die coating, lip coating, and comma coating.
A laminated film can be produced by bonding together a plurality of films using the adhesive for laminates according to one embodiment of the present invention. When the adhesive for laminates is applied to the films, the applied amount is preferably 0.5 to 10 g/m2, more preferably 1 to 5 g/m2.
The laminated film according to one embodiment of the present invention is a laminate obtained by bonding together a plurality of films using the above-described adhesive. FIGs. 1 and 2 each illustrate an example of one embodiment of the present invention; however, the present invention is not limited thereto.
FIG. 1 schematically illustrates a cross-section of a laminated film according to one embodiment of the present invention. A laminated film 10 is formed of two films and an adhesive 13 for laminated films that is interposed between the two films, and the two films 11 and 12 are bonded together by the adhesive 13 for laminated films. The films 11 and 12 may be made of the same material or different materials.
In FIG. 1, the two films 11 and 12 are bonded with each other; however, three or more films may be bonded together as well.
FIG. 2 schematically illustrates a cross-section of a laminated film according to another embodiment of the present invention. In FIG. 2, a thin film 11a is formed between the film 11 and the adhesive 13 for laminated films. For example, when the film 11 is a plastic film, FIG. 2 represents an embodiment in which a metal thin film 11a is formed on the surface of the film 11. The metal thin film 11a can be formed by, for example, vapor deposition on the surface of the plastic film 11, and the laminated film according to FIG. 2 can be obtained by bonding the film 11, on which the metal thin film 11a is formed, with the film 12 through the adhesive 13 for laminated films.
Examples of the metal to be vapor-deposited on the plastic film include aluminum, steel, and copper. By performing vapor deposition on the plastic film, the film can be imparted with a barrier property. As a vapor deposition material, for example, silicon oxide or aluminum oxide is used. The plastic film 11 used as a substrate may be transparent or colored in white, black, or the like.
As the film 12, for example, a plastic film formed of a polyvinyl chloride, a polyester, a fluororesin, an acrylic resin, or the like may be used and, for the purpose of imparting heat resistance, weather resistance, rigidity, insulating property and the like, it is particularly preferred to use, for example, a polyethylene terephthalate film or a polybutylene terephthalate film. The films 11 and 12 may be transparent or colored.
The vapor-deposited thin film 11a of the film 11 and the film 12 are bonded together using the adhesive 13 for laminated films according to one embodiment of the present invention; and, the films 11 and 12 are often laminated by a dry lamination method. Accordingly, the adhesive 13 for laminated films is required to be excellent in initial adherence to the films at the time of the lamination, as well as in adhesion to the films after curing.
The laminated film according to one embodiment of the present invention is used for the production of various packaging bags and outdoor materials.
The packaging bags refer to bag-like articles that are obtained by processing a laminated film for enclosure of a food item, a detergent, a shampoo, a conditioner, or the like therein. Examples of the outdoor materials include articles that are used outdoors, such as protective wall materials, roofing materials, solar cell modules, window materials, outdoor flooring materials, illumination protective materials, automobile members, and signboards.
These packaging bags and outdoor materials take a form that includes a laminated film obtained by bonding a plurality of films together.
The present invention will now be described more concretely and in more detail by way of Examples and Comparative Examples; however, the below-described Examples merely represent one emdobiment of the present invention, and the present invention is not limited by these Examples at any rate.
In the descriptions of Examples, unless otherwise specified, those parts where a solvent is not taken into account are basis of parts by mass or % by weight.
<Production of Adhesives for Laminates>
Components used for producing adhesives are shown below.
(A) Urethane Prepolymer Having Isocyanate Group at End
(A1) LOCTITE LIOFOL LA7735 (components: a polymer of a polyether polyol and a polyester polyol with an isocyanate monomer, NCO % by mass: 11.5%, manufactured by Henkel Japan Ltd.)
(A2) LOCTITE LIOFOL LA7715 (components: a polymer of a polyether polyol and an isocyanate monomer, NCO % by mass: 13.8%, manufactured by Henkel Japan Ltd.)
(B) Phenol-Based Compound Derived from Cashew Nut Shell Liquid
(B1) NX9201LP (CNSL polyester, manufactured by Cardolite Japan Ltd.)
(B2) NX9001LV (CNSL novolac, manufactured by Cardolite Japan Ltd.)
(B3) NX9016 (CNSL novolac, manufactured by Cardolite Japan Ltd.)
(C) Polyether Polyol
(C1) SANNIX PP400 (bifunctional polypropylene glycol, Mn: 400, hydroxyl value: 365 mgKOH/g, manufactured by Sanyo Chemical Industries, Ltd.)
(C2) EXCENOL 1020 (bifunctional polypropylene glycol, Mn: 1,000, hydroxyl value: 111 mgKOH/g, manufactured by AGC Inc.)
(C3) SANNIX GP1500 (trifunctional polyoxypropylene glyceryl ether, Mn: 1,500, hydroxyl value: 111 mgKOH/g, manufactured by Sanyo Chemical Industries, Ltd.)
(D) Tackifier Resin
(D1) QUINTONE 1500 (alicyclic petroleum resin, softening point: 100°C, manufactured by Zeon Corporation)
(D2) KOMOTAC KB90H (rosin ester, softening point: 90°C, acid value: 0 to 10 mgKOH/g, manufactured by Guangdong Komo Co., Ltd.)
(D3) SYLVALITE 9100 (rosin ester, softening point: 105°C, acid value: 7 mgKOH/g, manufactured by Kraton Corporation)
(E) Castor Oil-Based Compound
(E1) Industrial No. 1 castor oil (castor oil-based compound, manufactured by HOKOKU Corporation)
The components (A) to (E) were mixed as shown in Table 2 to produce adhesives for laminates of Examples 1 to 6 and Comparative Examples 1 to 3. Specifically, the components (B) to (E) were mixed in accordance with the respective formulations (parts by mass) shown in Table 2, followed by 1-hour stirring at 120°C. The resulting mixtures were allowed to cool, and the component (A) was subsequently added thereto. The added amount of the component (A) is the number of parts shown in Table 2. Thereafter, the mixtures of the components (A) to (E) were each stirred at 40°C for 5 minutes to prepare adhesives for laminates.

Figure JPOXMLDOC01-appb-T000004
<Production of Laminated Films>
The adhesives for laminates of Examples were each applied to the side of a solid-white printed surface of a PET film such that the applied adhesive had a solid mass of 2 g/m2. On the surface of this PET film to which the adhesive was applied (printed surface), another PET film having a surface that had been vapor-deposited with aluminum was laminated from the side of the vapor-deposited surface. Using a hand roller, the films were press-bonded such that voids between the adhesive and the vapor-deposited surface were removed as much as possible. Thereafter, the resultant was cured for 24 hours in a 40°C atmosphere to obtain a laminated film.
1. Measurement of Initial Viscosity
The initial viscosity of each adhesive for laminates was measured using a Brookfield viscometer in accordance with the method B of JAI 7-1991. Specifically, the viscosity at 40°C was measured using a No. 27 rotor at a rotation speed of 1 rpm.
The above-described apparatus was set up immediately after the preparation of the adhesive for laminates, and the viscosity at 1 minute after the start of the measurement (start of rotor rotation) was defined as the initial viscosity (also referred to as "η1").
2. Compatibility
The components (B), (C), (D), and (E) were mixed at the respective ratios shown in Table 2, and 50 g of the resulting mixture was added to a 140-ml transparent bottle and left to stand in the bottle for 3 hours (at 40°C), after which the presence or absence of separation was visually checked. The evaluation criteria were as follows.
◎: The transparency was high.
○: The transparency was slightly reduced.
△: The components were miscible, but the transparency was low.
×: The components were not miscible.
3. Measurement of Adhesive Strength
The above-obtained laminated films after 24-hour curing were each cut at a width of 15 mm in the TD direction and subjected to a peeling test using a tensile strength tester (TENSILON RTM-250 (trade name), manufactured by Orientec Co., Ltd.) to measure the adhesive strength.
The peeling test was conducted at a tensile speed of 300 mm/min under the T-type peeling condition after each laminated film was left to stand for at least 24 hours in a room-temperature environment (23°C). The evaluation criteria were as follows.
◎: The adhesive strength was 1.0 N/15 mm or more.
○: The adhesive strength was 0.75 N/15 mm or more but less than 1.0 N/15 mm
△: The adhesive strength was 0.5 N/15 mm or more but less than 0.75 N/15 mm
×: The adhesive strength was less than 0.5 N/15 mm.
-: It was difficult to measure the adhesive strength due to poor compatibility.
4. Evaluation of Appearance
The appearance of each of the above-obtained laminated films after 24-hour curing was visually evaluated. The evaluation criteria were as follows.
◎: No dot (void) was observed.
○: Dots (voids) were observed in a relatively small number.
△: Dots (voids) were present, but they were inconspicuous and presented no practical problem.
×: Dots (voids) were very conspicuous, or slight whitening was observed.
-: It was difficult to evaluate the appearance due to poor compatibility.
As shown in Table 2, the adhesives for laminates of Examples 1 to 6 not only were excellent in the compatibility of the components (A) and (E) and imparted films with an extremely high level of appearance, but also were excellent in adhesion to a film having a printed part and exhibited an excellent balance of performance.
The adhesive for laminates according to one embodiment of the present invention can be sufficiently utilized as, for example, an adhesive for laminates such as food packaging bags that are required to have an extremely high level of appearance.
On the other hand, as shown in Table 2, the adhesives for laminates of Comparative Examples 1 to 3 did not contain any phenol-based compound derived from a cashew nut shell liquid and thus could not improve the film appearance.
As described above, it was demonstrated that the adhesive for laminates according to one embodiment of the present invention is excellent in compatibility, exhibits an excellent adhesive strength without degrading the appearance of films, and has an excellent balance of performance.
The adhesive for laminates according to one embodiment of the present invention can be utilized in various applications since, when bonding a plurality of films together, the adhesive not only exhibits an excellent adhesive strength after curing without degrading the appearance of the films, but also is excellent in uniformity and inhibition of turbidity and has an excellent balance of performance. Particularly, the adhesive for laminates according to one embodiment of the present invention is suitable as an adhesive for a laminated film used for packaging a food item, a detergent, a shampoo, a conditioner, or the like.
Description of Symbols
10: laminated film
11: film
11a: vapor-deposited thin film
12: film
13: adhesive layer
Cross-Reference to Related Applications
This application claims benefit under Paris Convention of Japanese Patent Application No. 2021-175668 filed on October 27, 2021, incorporated herein by reference in its entirety.

Claims (9)

  1. An adhesive for laminates, comprising:
    (A) a urethane prepolymer having an isocyanate group at the end; and
    (B) a phenol-based compound derived from a cashew nut shell liquid.
  2. The adhesive for laminates according to claim 1, wherein the (B) phenol-based compound comprises a cardanol derivative.
  3. The adhesive for laminates according to claim 1 or 2, wherein the adhesive comprises the component (B) in an amount of 5 to 70 parts by mass per 100 parts by mass of the total mass of the components (A) and (B).
  4. The adhesive for laminates according to any one of claims 1 to 3, further comprising (C) a polyether polyol.
  5. The adhesive for laminates according to claim 4, wherein the (C) polyether polyol comprises a polypropylene glycol having a number average molecular weight of 300 to 2,000.
  6. The adhesive for laminates according to any one of claims 1 to 5, further comprising (D) a tackifier resin.
  7. The adhesive for laminates according to calim 6, wherein the (D) tackifier resin comprises a natural resin having a softening point of 80 to 120°C.
  8. The adhesive for laminates according to claim 7, wherein the natural resin comprises a rosin ester.
  9. A laminated film in which a plurality of films are bonded through the adhesive for laminates according to any one of claims 1 to 8.

PCT/JP2022/039668 2021-10-27 2022-10-25 Adhesive for laminates WO2023074667A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2018197329A (en) * 2017-05-25 2018-12-13 株式会社カネカ Room temperature-curable composition
JP2020041082A (en) * 2018-09-12 2020-03-19 株式会社イノアック技術研究所 Moisture-curable adhesive
WO2020163413A1 (en) * 2019-02-05 2020-08-13 Franklin International, Inc. Very high solids, thermoset composition with one-side (wet set) adhesion to unprimed/unmodified tpo surfaces

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2018197329A (en) * 2017-05-25 2018-12-13 株式会社カネカ Room temperature-curable composition
JP2020041082A (en) * 2018-09-12 2020-03-19 株式会社イノアック技術研究所 Moisture-curable adhesive
WO2020163413A1 (en) * 2019-02-05 2020-08-13 Franklin International, Inc. Very high solids, thermoset composition with one-side (wet set) adhesion to unprimed/unmodified tpo surfaces

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