JP2011093975A - Adhesive composition for laminated sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition which enables strong adhesion with long-term durability between an untreated plastic film surface and another base material such as a metal or plastic, circumstantially, which suppresses deterioration with age in the adhesive strength of a sheet formed by adhesion of an untreated plastic film surface to another base material and exposed outdoor, and can maintain the adhesive strength over a long period of time. <P>SOLUTION: The adhesive composition for a laminated sheet contains a polyol (A) having a number-average molecular weight of 5,000-50,000 and a modified polyisocyanate (B') prepared by modifying 20-80 wt.% in 100 wt.% of a polyisocyanate (B) having 2.5-7 isocyanate groups on average in one molecule with a blocking agent (C). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an adhesive composition for laminated sheets used for bonding plastic films, metal foils and the like.

  In recent years, aluminum as a multilayer (composite) sheet used for outdoor industrial applications, for example, barrier materials, roofing materials, solar cell panel materials, window materials, outdoor flooring materials, lighting protection materials, automobile members, signboards, stickers, etc. , Copper or steel sheet metal foil, metal plate, or metal vapor deposition film and polypropylene, polyvinyl chloride, polyester, fluororesin, acrylic resin, or other plastic film were laminated to form a laminated film Things have been used. As an adhesive composition for bonding a metal foil, a metal plate, or a metal vapor-deposited film, and a plastic film in these multilayer films, a polyepoxy adhesive composition or a polyurethane adhesive composition is known. ing.

  Patent Document 1 discloses a polyester resin in consideration of balance that can give excellent initial cohesion and adhesion, and a polyurethane resin adhesive composition using the polyester resin.

  Patent Document 2 discloses a polyurethane adhesive composition that is excellent in hot water resistance during retort sterilization in food packaging.

  Patent Document 3 discloses that a polyurethane adhesive composition having hydrolysis resistance is used in a solar cell back surface sealing sheet.

  Furthermore, Patent Document 4 discloses a solar cell back surface sealing sheet including an adhesion improving layer made of a polyester resin or a polyester polyurethane resin.

  On the other hand, efforts to combat global warming have become urgent in recent years, and it has been required to develop and provide long-lasting materials for components such as solar cell backside sealing sheets and laminated sheets. In order to obtain the above, it has been required to laminate a plurality of various plastic films. When laminating a plurality of plastic films, it is necessary to bond so-called plastic film untreated surfaces that have not been subjected to treatment for improving the adhesive strength such as corona treatment.

  However, the urethane-based adhesive of the above prior art has a problem that a strong and long-lasting adhesive cannot be applied between the untreated surface of the plastic film and another substrate such as plastic or metal. . Moreover, when bonding untreated plastic film surfaces, it has been extremely difficult to achieve both sufficient adhesive strength and long-term durability.

JP-A-10-218978 Japanese Patent Laid-Open No. 06-116542 JP 2008-4691 A JP 2007-136911 A

  The present invention can provide a strong and long-lasting adhesion between the untreated surface of the plastic film and another substrate such as plastic, metal, and the like. It is an object of the present invention to provide an adhesive composition that can suppress a decrease in adhesive strength over time during outdoor exposure of a sheet adhered to a base material and can maintain the adhesive strength over a long period of time.

   As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the following adhesive composition for laminated sheets, and have completed the present invention. That is, the first invention of the present invention is a polyol (A) having a number average molecular weight of 5,000 to 50,000 and a polyisocyanate having an average of 2.5 to 7 isocyanate groups in one molecule ( B) The present invention relates to an adhesive composition for laminated sheets containing a modified polyisocyanate (B ′) obtained by modifying 20 to 80% by weight of 100% by weight with a blocking agent (C).

  In the second invention, the blocking agent (C) is at least one selected from the group consisting of ε-caprolactam, methyl ethyl ketone oxime, pyrazole compounds, malonic acid diesters, and acetylated ketone compounds. It is related with the adhesive composition for laminated sheets of 1 invention.

  Moreover, 3rd invention is related with the adhesive composition for laminated sheets of 1st or 2nd invention which contains 20-50 weight part of epoxy resins (D) with respect to 100 weight part of polyol (A).

  Moreover, 4th invention is related with the adhesive composition for laminated sheets of 3rd invention whose number average molecular weights of an epoxy resin (D) are 300-5,000.

  The fifth invention is the invention according to any one of the first to fourth inventions, wherein the polyisocyanate (B) is at least one selected from a polyisocyanate derived from hexamethylene diisocyanate and a polyisocyanate derived from isophorone diisocyanate. The present invention relates to an adhesive for laminated sheets.

  Moreover, 6th invention is the adhesive for laminated sheets of the 1st-5th invention which contains 0.1-5 weight part of silane coupling agents (E) with respect to 100 weight part of polyols (A). Relates to the composition.

  The seventh invention relates to the adhesive composition for laminated sheets according to any one of the first to sixth inventions, wherein the isocyanate group concentration in the polyisocyanate (B) is 10 to 30% by weight.

  The eighth invention relates to a laminate using the adhesive composition for laminated sheets of any one of the first to seventh inventions.

  Moreover, 9th invention is related with the solar cell back surface protection sheet using the adhesive composition for laminated sheets of any one of 1st-7th invention.

  By using the adhesive composition for laminated sheets of the present invention as an adhesive for laminated sheets, strong and long-lasting adhesion between the untreated plastic film surface and other substrates such as plastic and metal More specifically, it is possible to suppress a decrease in the adhesive strength over time when the sheet having the untreated surface of the plastic film bonded to another substrate is exposed outdoors, and to maintain the adhesive strength over a long period of time. An adhesive composition could be provided.

  The adhesive composition for laminated sheets of the present invention contains a polyisocyanate (B) having an average of 2.5 to 7 isocyanate groups in one molecule (hereinafter also simply referred to as “polyisocyanate (B)”). By modifying a part of the isocyanate group with the blocking agent (C) to obtain a modified blocked isocyanate (B ′) and controlling the crosslink density in the adhesive layer formed from the adhesive composition, Sufficient initial adhesive force and cohesive force can be obtained when the treated surface and another substrate are bonded.

  Moreover, the laminated body which bonded the untreated surface of the plastic film to another substrate using the adhesive composition of the present invention is subjected to a heat treatment for removing the blocking agent (C) in the modified blocked isocyanate (B ′). By applying, the blocking agent (C) of the modified blocked isocyanate (B ′) is removed, and then the isocyanate from which the blocking agent (C) is removed causes a curing reaction at a high temperature, so that the untreated surface of the plastic film and other surfaces The adhesive strength can be maintained over a long period of time by suppressing a decrease in the adhesive strength over time when the sheet adhered to the substrate is exposed outdoors.

  The heat treatment conditions for removing the blocking agent (C) in the modified blocked isocyanate (B ′) are not particularly limited as long as the blocking agent (C) is removed, but it is preferably 100 ° C. or higher. More preferably, the temperature is 120 ° C. or higher. Further, the heat treatment time is preferably 5 minutes or more, and more preferably 10 minutes or more. If heat treatment is performed at a very high temperature for a long time, the polyol (A) or the like in the plastic film or the adhesive composition may deteriorate and cause a problem.

  Moreover, when using the adhesive composition of this invention for the protection sheet for solar cell panel materials, it is heat-processed at the temperature of about 140 degreeC for about 15 to 30 minutes in a solar cell manufacturing process. In this case, there is no need to newly add a heat treatment step. Therefore, it can be said that the adhesive composition of the present invention is suitable as an adhesive for a protective sheet for a solar cell panel material, particularly as an adhesive for a solar cell back surface protective sheet.

  The isocyanate from which the blocking agent (C) is removed causes a curing reaction at high temperatures, thereby suppressing a decrease in adhesive strength over time during outdoor exposure of a sheet bonded to an untreated plastic film surface and another substrate. The mechanism that can maintain the adhesive strength over a long period of time is not clear, but by reacting at a high temperature, the hydroxyl group on the surface of the plastic film (for example, PET film) reacts with the isocyanate group, or at a high temperature. As a result of the extremely active movement of the compounds constituting the plastic film and the adhesive composition at the molecular level, the wetting and anchoring effect of the adhesive composition on the base material is improved and the adhesive strength is increased. Conceivable.

  The adhesive composition for laminated sheets of the present invention includes a polyol (A) having a number average molecular weight of 5,000 to 50,000 (hereinafter, also simply referred to as “polyol (A)”), and one molecule. It contains a modified polyisocyanate (B ′) obtained by modifying 20 to 80% by weight of 100% by weight of polyisocyanate (B) having an average of 2.5 to 7 isocyanate groups with a blocking agent (C). It is characterized by.

<Polyol (A)>
The polyol (A) is not limited to the following, and examples thereof include polyester polyol, polyurethane polyol, polyether polyol, polycarbonate polyol, polyester polyurethane polyol, polyether polyurethane polyol, polycarbonate polyurethane polyol, and polyacryl polyol. One or more of these polyols can be used. From the viewpoints of adhesive strength, durability, and workability, polyester polyol, polyester polyurethane polyol, polycarbonate polyurethane polyol, and polyacryl polyol are preferable.

  The number average molecular weight of the polyol (A) in the present invention needs to be 5,000 to 50,000. If it is less than 5,000, the initial cohesive force is lowered. Moreover, when it exceeds 50,000, the solubility of a resin, a viscosity, and the applicability | paintability (handleability) of an adhesive agent will fall. The number average molecular weight of the polyol (A) is preferably 8,000 to 30,000. If it is within this range, the problem of tunneling during lamination hardly occurs, and an appropriate coating viscosity can be obtained, so that the coating method is not limited.

  The polyol (A) can be used by reacting two or more different polyols. In this case, there is a possibility that good characteristics of different types of polyols can be obtained, and an adhesive composition having better characteristics can be obtained.

<Polyisocyanate (B)>
The polyisocyanate (B) is not limited to the following, but is preferably a compound derived from a known diisocyanate. For example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, bis (4-isocyanatocyclohexyl) methane, or water Compounds derived from diisocyanates such as added diphenylmethane diisocyanate, that is, the diisocyanate nurate, trimethylolpropane adduct, biuret, prepolymer having an isocyanate residue (low polymer obtained from diisocyanate and polyol), isocyanate residue Uretdione isomers having all groups, allophanate isomers, or complexes thereof, and the like. It can be used in two or more. Especially, since it is used also for an outdoor use, it is preferable to use an aliphatic or alicyclic isocyanate, or its derivative (s) in order to reduce yellowing with time. Among them, it is particularly preferable to use a polyisocyanate derived from isophorone diisocyanate or a polyisocyanate derived from hexamethylene diisocyanate, and from the viewpoint of producing an initial cohesive force, it was derived from hexamethylene diisocyanate. It is preferable to use polyisocyanate.

  The number of isocyanate groups in the polyisocyanate (B) is 2.5 to 7 on average in one molecule, and preferably 2.7 to 3.7. When the number is less than 2.5, a sufficient amount of cross-linking cannot be obtained to obtain cohesive strength as an adhesive, and as a result, sufficient adhesive strength and long-term durability cannot be obtained. When the number is more than 7, the crosslink density of the adhesive is increased, and the adhesion during lamination is lowered. In addition, the pot life is very short, making it difficult to use.

  The isocyanate group concentration in the polyisocyanate (B) is preferably 10 to 30% by weight, and more preferably 11 to 25% by weight. In addition, the isocyanate group density | concentration in polyisocyanate (B) can be calculated | required by the titration method.

  Moreover, it is preferable that the usage-amount of polyisocyanate (B) is 7-35 weight part with respect to 100 weight part of polyols (A), and also it is preferable that it is 10-25 weight part. If it is less than 7 parts by weight, the adhesive strength after indoor and outdoor exposure may decrease. On the other hand, if it exceeds 35 weight, the initial adhesive strength may be lowered.

<Blocking agent (C)>
As described above, the blocking agent (C) is used to remove the blocking agent at the initial stage, that is, before the indoor / outdoor exposure, when the plastic film untreated surface is bonded to another substrate. It is a compound used to modify a part of the isocyanate groups in the polyisocyanate (B) in order to achieve both indoor exposure resistance after heat treatment. As a ratio to be modified, it is necessary that 20 to 80% by weight in 100% by weight of polyisocyanate (B) is modified with a blocking agent (C), and 30 to 70% by weight is a blocking agent ( C) is preferably modified, and 35 to 65% by weight is more preferably modified with the blocking agent (C). If it is less than 20% by weight, sufficient indoor exposure resistance after heat treatment cannot be obtained. On the other hand, if the amount is more than 80% by weight, sufficient adhesive strength and cohesive strength at the initial stage, that is, before heat treatment cannot be obtained.

  As the blocking agent (C), it is preferable to use at least one compound selected from the group consisting of ε-caprolactam, methyl ethyl ketone oxime, pyrazole compounds, malonic acid diesters, and acetylated ketone compounds, It is not limited to these, and any material that reacts with the polyisocyanate (B) to form a block body and then deviates by heat treatment can be used. The said compound is preferably used in order to suppress the deterioration of the plastic base material by heat processing, when using the adhesive composition of this invention for a plastic base material. Examples of the pyrazole-based compound include 1,2-pyrazole, 1,2,4-triazole, diisopropylamine, 3,5-dimethylpyrazole, and the like. Examples of malonic acid diesters include dimethyl malonate, diethyl malonate, and dipropyl malonate. Examples of the acetylated ketone compound include acetylacetone.

  Further, when the adhesive composition of the present invention is used for a solar cell panel material protective sheet such as a solar cell back surface protective sheet, as described above, in the solar cell manufacturing process, the temperature is about 140 ° C. from 15 minutes. Since it is heat-treated for about 30 minutes, pyrazole compounds such as methyl ethyl ketone oxime, 1,2-pyrazole, 1,2,4-triazole, diisopropylamine, 3,5-dimethylpyrazole, etc. Particularly preferred are diethyl acid and acetylacetone.

<Epoxy resin (D)>
From the viewpoint of hydrolysis resistance, the adhesive composition for laminated sheets of the present invention contains an epoxy resin (D) as a resin that reacts with a carboxyl group produced by hydrolysis of an ester bond in the polyol (A). It is preferable to make it. The epoxy resin (D) has an effect of improving the heat and moisture resistance.

  The epoxy resin (D) is not limited to the following, but is bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol fluorenediglycidyl ether, biscresol. Full orange glycidyl ether, bisphenoxyethanol full orange glycidyl ether, glycerol triglycidyl ether, glycerol diglycidyl ether, polyglycerol polyglycidyl ether, 1,6-butanediol diglycidyl ether, bisphenol A diglycidyl ether, propylene oxide modified bisphenol A Diglycidyl ether, bisphenol F diglycidyl ether, epichlorohydrin modified phthalic acid, Examples include chlorohydrin-modified hexahydrophthalic acid, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and one or more of these can be used. . When used as a component of a two-component adhesive composition, it is preferably used as a main agent together with the polyol (A).

  Among the epoxy resins (D), epoxy resins having a number average molecular weight of 300 to 5,000 are preferable from the viewpoints of adhesive strength and heat and humidity resistance. As an epoxy resin having a number average molecular weight of 300 to 5000, for example, a commercially available product is not limited to the following, but is manufactured by Japan Epoxy Resin, Epicoat 825, 827, 828, 834, 1001, 1002, 1003, 1055. , 1004, 1007, 806, 807, or 4004 series, manufactured by Toto Kasei Co., Ltd., YD-127, YD-128, YD-115, YD-134, YD-011, YD-012, YD-013, YD- 014, YD-017, YD-019, manufactured by Adeka, Adeka Resin EP-4100, 4300, 4340, 4200, 4400, 4500, 4510, 4520, 4530, 4901, 4930, 4950, 5100, 4000, 4005, 1307, 4004 4080 or 4092 series Or DIC Corporation, Epicron 152, 153, 1121N, 1123N, N-660, N-665, N-670, N-673, N-680, N-695, N-660, N-672, N -662, N-655, N-673, 850, 830, 4032, 7120, 7015, or 7200 series.

  The blending amount of the epoxy resin (D) is preferably 20 to 50 parts by weight with respect to 100 parts by weight of the polyol (A) from the viewpoints of adhesive strength and heat and humidity resistance. More preferably, it is 20-40 weight part. If it is less than 20 parts by weight, the effect of improving the heat and moisture resistance is not sufficient, and if it exceeds 50 parts by weight, the adhesive becomes hard and the adhesiveness may be lowered.

<Silane coupling agent (E)>
The adhesive composition for laminated sheets of the present invention contains a silane coupling agent (E) from the viewpoint of improving adhesive strength when using a metal foil, a metal plate, a metal vapor-deposited film or the like as a base material. Is preferred.

Examples of the silane coupling agent (E) include, but are not limited to, vinyl silanes such as vinyl tris (β-methoxyethoxy) silane, vinyl ethoxy silane, and vinyl trimethoxy silane;
(meth) acryloxysilanes such as γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, and γ- (meth) acryloxypropyldimethoxymethylsilane;
β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) methyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, β- (3, Epoxy silanes such as 4-epoxycyclohexyl) methyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-glycidoxypropyltriethoxysilane;
N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldiethoxysilane, γ-amino Aminosilanes such as propyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, and N-phenyl-γ-aminopropyltriethoxysilane;
In addition, thiosilanes such as γ-mercaptopropyltrimethoxysilane and γ-mercaptopropyltriethoxysilane are exemplified. These may be used alone or in any combination of two or more. “(Meth) acryloxy” means “acryloxy” or “methacryloxy”.

  The addition amount of the silane coupling agent (E) is preferably 0.1 to 5 parts by weight and more preferably 1 to 3 parts by weight with respect to 100 parts by weight of the polyol (A). If it is less than 0.1 part by weight, the effect of improving the adhesive strength to the metal foil by adding a silane coupling agent is poor, and even if it is added by 5 parts by weight or more, further improvement in performance may not be observed.

  The adhesive composition for laminated sheets of the present invention may be a so-called two-liquid mixed type adhesive in which the main agent and the curing agent are mixed at the time of use, or one liquid in which the main agent and the curing agent are mixed in advance. It may be a type of adhesive. Furthermore, the type which mixes a several main ingredient and / or several hardening | curing agent at the time of use may be sufficient. Usually, the main agent contains polyol (A), if necessary, other polyol, silane coupling agent (E), epoxy resin (D), organic solvent, and other additives, and the curing agent is modified polyisocyanate. (B ′) If necessary, an organic solvent and other additives are included.

  Examples of other polyols include ethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, butylene glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, and 3,3′-. Dimethylol heptane, polyoxyethylene glycol, polyoxypropylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, octanediol, butylethylpentanediol, 2-ethyl-1,3-hexanediol , Cyclohexanediol, bisphenol A, bisphenol F, and the like, and compounds having two hydroxyl groups such as glycerin, trimethylolpropane, pentaerythritol and the like. Compounds having the like.

  As other additives, phosphoric acid compounds such as phosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorous acid and esters thereof can be added to improve metal adhesion.

  The adhesive composition of the present invention can also be used as an anchor coating agent for solar cell laminate sheets. In that case, it is preferable to add an antiblocking agent.

In addition, additives known for adhesives can be added to the main agent, and for example, a reaction accelerator can be used. Specifically, metal catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dimaleate;
1,8-diaza-bicyclo (5,4,0) undecene-7,1,5-diazabicyclo (4,3,0) nonene-5,6-dibutylamino-1,8-diazabicyclo (5,4,0 ) Tertiary amines such as undecene-7;
Examples include reactive tertiary amines such as triethanolamine, and one or more reaction accelerators selected from these groups can be used.

  For the purpose of improving the laminate appearance, a known leveling agent or antifoaming agent may be added to the main agent.

  Examples of leveling agents include polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyester-modified hydroxyl group-containing polydimethylsiloxane, polyetherester-modified hydroxyl group-containing polydimethylsiloxane, and acrylic copolymers. , Methacrylic copolymers, polyether-modified polymethylalkylsiloxanes, acrylic acid alkyl ester copolymers, methacrylic acid alkyl ester copolymers, lecithin, or mixtures thereof.

  Examples of the antifoaming agent include known resins such as silicone resins, silicone solutions, copolymers of alkyl vinyl ethers, alkyl acrylates and alkyl methacrylates, or mixtures thereof.

  As the curing agent, in addition to the modified polyisocyanate (B ′), a known oxazoline compound such as 2,5-dimethyl-2-oxazoline or 2 is optionally added within a range not inhibiting the effects of the present invention. , 2- (1,4-butylene) -bis (2-oxazoline) or a hydrazide compound such as isophthalic acid dihydrazide, sebacic acid dihydrazide, or adipic acid dihydrazide.

  Moreover, the adhesive composition for laminated sheets of this invention can contain a well-known organic solvent, and can be used as an organic solvent solution. Examples of the organic solvent include, but are not limited to, ester solvents such as ethyl acetate or butyl acetate, or ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, or cyclohexanone. Two or more kinds can be mixed and used.

In order to produce a laminate such as a multilayer film using the adhesive composition according to the present invention, a commonly used method can be employed. For example, the adhesive composition is applied to one side of a plastic film or the like which is one laminate substrate by a comma coater or a dry laminator, and the solvent is volatilized as necessary, and then bonded to the other laminate substrate, Curing may be performed at room temperature or under heating. The amount of adhesive applied to the surface of the laminate substrate is preferably about 1 to 50 g / m ^{2 in} terms of dry. As a laminate base material, an arbitrary base material can be selected in any number depending on the application, and when making a multilayer structure of three or more layers, all or a part of each layer is bonded. The adhesive composition according to the present invention can be used.

  In producing a multilayer film, in order to bring out the excellent characteristics of the adhesive composition according to the present invention, for example, untreated surfaces of various films such as PET film, PEN film, and fluorine film, and olefin groups such as polypropylene It is preferable to apply and use it on a substrate or a film surface that is extremely difficult to bond with a general adhesive composition such as a material.

Hereinafter, the present invention will be described more specifically with reference to examples. In the examples, “part” means “part by weight” and “%” means “% by weight”. The unit of hydroxyl value is mgKOH / g, and the unit of acid value is mgKOH / g.
Moreover, the value of a number average molecular weight is a polystyrene conversion value by GPC (gel permeation chromatography).

Production Example 1 <Polyol a>
(Polyester polyol having a bifunctional terminal primary hydroxyl group and a number average molecular weight of 10,000)
A reactor was charged with 31.5 parts of isophthalic acid, 27.7 parts of adipic acid, 7.1 parts of ethylene glycol, 15.8 parts of neopentyl glycol, and 17.9 parts of 1,6-hexanediol. While stirring, the mixture was gradually heated to 160 to 240 ° C. to carry out an esterification reaction. The reaction was carried out at 240 ° C. for 1 hour, and the acid value was measured. When the acid value became 15 or less, the reaction vessel was gradually depressurized to 1 to 2 Torr, and the reaction was stopped when the predetermined viscosity was reached. The number average molecular weight of the obtained polyester polyol was 10,000 as a result of GPC measurement. The hydroxyl value was 11.2 and the acid value was 0.2.

Production Example 2 <Polyol b>
(Polyester polyol having a bifunctional terminal primary hydroxyl group and a number average molecular weight of 40,000)
21.5 parts of isophthalic acid, 37.7 parts of adipic acid, 7.1 parts of ethylene glycol, 15.8 parts of neopentyl glycol, and 17.9 parts of 1,6-hexanediol were charged into a reaction vessel under a nitrogen stream. While stirring, the mixture was gradually heated to 160 to 240 ° C. to carry out an esterification reaction. The reaction was carried out at 240 ° C. for 1 hour, and the acid value was measured. When the acid value became 15 or less, the reaction vessel was gradually depressurized to 1 to 2 Torr, and the reaction was stopped when the predetermined viscosity was reached. The number average molecular weight of the obtained polyester polyol was 40,000 as a result of GPC measurement. The hydroxyl value was 11.2 and the acid value was 0.2.

Production Example 3 <Polyol c>
(Polycarbonate polyurethane polyol whose terminal primary hydroxyl group is bifunctional and has a number average molecular weight of 10,000)
100 parts of polycarbonate diol having a molecular weight of 2,000 (manufactured by Daicel Chemical Industries, Plaxel CD CD220PL) and 6.7 parts of hexamethylene diisocyanate were reacted in a nitrogen atmosphere at 100 ° C. in 100 parts of ethyl acetate for 48 hours with stirring. The number average molecular weight of the obtained polycarbonate polyurethane polyol was 10,000 as a result of GPC measurement. The hydroxyl value was 11.0 and the acid value was 0.0.

Production Example 4 <Polyol d>
(Polycarbonate polyurethane polyol with terminal primary hydroxyl group bifunctional and number average molecular weight 6,000)
100 parts of polycarbonate diol having a molecular weight of 2,000 (manufactured by Daicel Chemical Industries, Plaxel CD CD220PL) and 11.2 parts of hexamethylene diisocyanate were reacted in a nitrogen atmosphere at 100 ° C. in 100 parts of ethyl acetate with stirring for 48 hours. The number average molecular weight of the obtained polycarbonate polyurethane polyol was 6,000 as a result of GPC measurement. The hydroxyl value was 11.0 and the acid value was 0.0.

Production Example 5 <Polyol e>
(Polyester polyol having a bifunctional terminal primary hydroxyl group and a number average molecular weight of 4000)
15.4 parts terephthalic acid, 16.1 parts isophthalic acid, 27.7 parts adipic acid, 7.1 parts ethylene glycol, 15.8 parts neopentyl glycol, and 17.9 parts 1,6-hexanediol The mixture was gradually heated to 160 to 240 ° C. with stirring under a nitrogen stream to carry out an esterification reaction. The reaction was conducted at 240 ° C. for 1 hour, and the acid value was measured. When the acid value became 15 or less, the reaction vessel was gradually depressurized to 1 to 2 Torr, and when the predetermined viscosity was reached, the reaction was stopped and taken out. The number average molecular weight of the obtained polyester polyol was 4,000 as a result of GPC measurement. The hydroxyl value was 28.1 and the acid value was 0.1.

Production Example 6 <Main agent 1>
100 parts of polyol a obtained in Production Example 1, 30 parts of bisphenol A type epoxy resin [manufactured by Toto Kasei Co., Ltd., YD-012], 1 part of silane coupling agent KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.) and catalyst Then, 0.005 part of dioctyltin dilaurate and 130 parts of ethyl acetate were added, and the mixture was heated, dissolved, and mixed at 70 ° C. A resin solution having a solid content of 50% obtained by finely adjusting the solid content with ethyl acetate is used as the main agent 1.

Production Example 7 <Main agent 2>
100 parts of polyol b obtained in Production Example 2, 30 parts of bisphenol A type epoxy resin [manufactured by Toto Kasei Co., Ltd., YD-017], 1 part of silane coupling agent KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.) and catalyst Then, 0.005 part of dioctyltin dilaurate and 130 parts of ethyl acetate were added, and the mixture was heated, dissolved, and mixed at 70 ° C. A resin solution having a solid content of 50% obtained by finely adjusting the solid content with ethyl acetate is used as the main agent 2.

Production Example 8 <Main agent 3>
100 parts of polyol c obtained in Production Example 3, 30 parts of bisphenol A type epoxy resin [manufactured by Toto Kasei Co., Ltd., YD-014], 1 part of silane coupling agent KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.) and catalyst Then, 0.005 part of dioctyltin dilaurate and 130 parts of ethyl acetate were added, and the mixture was heated, dissolved, and mixed at 70 ° C. A resin solution having a solid content of 50% obtained by finely adjusting the solid content with ethyl acetate is used as the main agent 3.

Production Example 9 <Main agent 4>
100 parts of polyol d obtained in Production Example 3, bisphenol A type epoxy resin [manufactured by Toto Kasei Co., Ltd., YD-012], 1 part of silane coupling agent KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.) and catalyst Then, 0.005 part of dioctyltin dilaurate and 130 parts of ethyl acetate were added, and the mixture was heated, dissolved, and mixed at 70 ° C. A resin solution having a solid content of 50% obtained by finely adjusting the solid content with ethyl acetate is used as the main agent 4.

Production Example 10 <Main agent 5>
100 parts of polyol e obtained in Production Example 5, 30 parts of bisphenol A type epoxy resin [manufactured by Tohto Kasei Co., Ltd., YD-012], 1 part of silane coupling agent KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.) and catalyst Then, 0.005 part of dioctyltin dilaurate and 130 parts of ethyl acetate were added, and the mixture was heated, dissolved, and mixed at 70 ° C. A resin solution having a solid content of 50% obtained by finely adjusting the solid content with ethyl acetate is used as the main agent 5.

Production Example 11 <Curing Agent 1>
30 parts of an isocyanate curing agent having an average of 6 isocyanate groups and an isocyanate concentration of 18.9% by weight [Duranate MHG80 (Asahi Kasei Co., Ltd.)], 30 parts of an isocyanurate type trimer of isophorone diisocyanate, isocyanurate of isophorone diisocyanate Curing agent 1 is obtained by diluting block isocyanate obtained by blocking 40 parts of a nurate type trimer with methyl ethyl ketone oxime with ethyl acetate to give a resin solution having a solid content of 50%.

Production Example 12 <Curing Agent 2>
30 parts of isocyanate curing agent Duranate MHG80 (Asahi Kasei Co., Ltd.)] having an average of 6 isocyanate groups and an isocyanate concentration of 18.9% by weight, and 70 parts of an isocyanurate type trimer of isophorone diisocyanate were blocked with methyl ethyl ketone oxime. The hardened agent is obtained by diluting the blocked isocyanate with ethyl acetate to give a resin solution having a solid content of 50%.

Production Example 13 <Curing Agent 3>
20 parts of an isocyanate curing agent [Duranate MHG80 (Asahi Kasei Co., Ltd.)] having an average of 6 isocyanate groups and an isocyanate concentration of 18.9% by weight, 1 part of 10 parts of the isocyanate curing agent [Duranate MHG80 (Asahi Kasei Co., Ltd.)] , Block isocyanates blocked with 2-pyrazole, 70 parts of isocyanurate type trimer of isophorone diisocyanate blocked with methyl ethyl ketone oxime, diluted with ethyl acetate to give a resin solution with a solid content of 50% Agent 3 is used.

Production Example 14 <Curing Agent 4>
30 parts of an isocyanate curing agent having an average of 6 isocyanate groups and an isocyanate concentration of 18.9% by weight [Duranate MHG80 (manufactured by Asahi Kasei Co., Ltd.)], 53 parts of an isocyanurate type trimer of isophorone diisocyanate, and an isocyanate of isophorone diisocyanate A hardened agent 4 is a blocked isocyanate obtained by diluting 17 parts of a nurate-type trimer with 1,2-pyrazole with ethyl acetate to give a resin solution having a solid content of 50%.

<Adhesive composition>
Examples 1-8 and Comparative Examples 1-10
Main agents 1 to 5 obtained in Production Examples 6 to 10 and curing agents 1 to 4 obtained in Production Examples 11 to 14 were blended according to the combinations shown in Table 1 to obtain adhesive compositions. The blending amount was the main component: polyisocyanate (B) used for the production of the curing agent = 100: 15 (weight ratio in terms of solid content).

  Table 1 shows the combinations of the main agent and the curing agent in Examples 1 to 8 and Comparative Examples 1 to 10, and the adhesive strength before and after the heat treatment and before and after the 85 ° C. hot water immersion.

<Evaluation>
Using each adhesive composition of Examples and Comparative Examples, the untreated surfaces of a polyethylene terephthalate (PET) film as a base material are laminated together to produce a laminated film (laminate material), and measurement of adhesive strength before heat treatment And the measurement of adhesive strength before and after the wet heat resistance test was tested. In Table 1, what is written as cf next to the numerical value of the adhesive strength is a product in which the adhesive layer causes cohesive failure when measuring the adhesive force. Even if the adhesive strength is in a practical range, the material that cohesively breaks is a problem because the base material laminated at the time of heat treatment is peeled off or the base materials are displaced from each other because of lack of heat resistance. A specific evaluation method will be described below.

After applying the adhesive composition to a polyester film [Toray Industries, Ltd., Lumirror X-10S, thickness 250 μm] with a dry laminator in an amount of ⁴ to 5 g / m ^2, and volatilizing the solvent. And laminated on an aluminum foil (thickness 50 μm). Thereafter, after curing (aging) at 40 ° C. for 3 days to cure the adhesive, heat treatment at 140 ° C. for 30 minutes (denoted as heat treatment in Table 1) is performed to remove the blocking agent, and the following: The test was conducted.

  The obtained multilayer film was put into a glass bottle, the entire multilayer film was immersed in distilled water, and the container was sealed. This was aged at 85 ° C. for 10 days, 20 days, and 30 days to obtain a heat and humidity resistance test assuming outdoor exposure.

  Each multi-layered film after aging was cut into a size of 200 mm × 15 mm, dried at room temperature for 6 hours, and then subjected to a T-type peel test at a load rate of 300 mm / min using a tensile tester according to the test method of ASTM D1876-61. I did it. The peel strength (N / 15 mm width) between the polyester film and the aluminum foil was shown as an average value of five test pieces.

The evaluation is as follows. Before heat treatment at 140 ° C. for 30 minutes and after aging for 30 days in distilled water at 85 ° C.,
Practical range: 2 N / 15 mm or more and the adhesive layer does not cause cohesive failure.
Not practical: Less than 2 N / 15 mm or cohesive failure of the adhesive layer.
Those having an adhesive strength of 2N / 15 mm or more, which cause cohesive failure, are problematic because the base materials bonded together during heat treatment are peeled off or the base materials are displaced.

  As shown in Table 1, the adhesive compositions of the examples were excellent in adhesive strength before and after the heat treatment and after the hot water test, and were able to maintain the adhesive strength over a long period of time. Since this test method promotes hydrolysis, it is considered to be a stricter test method with respect to moisture and heat resistance than an outdoor exposure test that is left outdoors. Therefore, it is considered that the adhesive compositions of these examples are excellent in long-term wet heat resistance for outdoor use.

  For example, in JIS C 8917 (environmental test method and durability test method of crystalline solar cell module), a moisture resistance test B-2 is defined that it is durable for 1000 hours under 85 ° C. and 85% RH, It is known as a particularly severe test method. In this application, a test was performed in 85 ° C. warm water, but this test was severer than JIS C 8917, and the adhesive compositions of these examples having long-term wet heat resistance are solar cells having a multilayer structure. It means that it is suitable as an adhesive composition used between the sheet layers of the back protective sheet.

  In such a long-term moisture and heat resistance test, the solar cell back surface protection sheet retains sufficient interlayer adhesion strength (laminate strength) and does not cause delamination between the sheet layers, thereby protecting solar cell elements and maintaining power generation efficiency. Furthermore, it can contribute to the extension of the lifetime of the solar cell. Extending the lifetime of solar cells leads to the spread of solar cell systems and contributes to environmental conservation from the viewpoint of securing energy other than fossil fuels.

  The adhesive composition according to the present invention is a multi-layer laminate for outdoor industrial applications such as buildings (barriers, roofing materials, solar cell panel materials, window materials, outdoor flooring materials, certification protective materials, automobile members, etc.). Strong adhesive strength can be provided as an agent, and a decrease in adhesive strength over time due to hydrolysis or the like during outdoor exposure can be suppressed, and strong adhesive strength can be maintained over a long period of time.

Claims (9)

  Polyol (A) having a number average molecular weight of 5,000 to 50,000, and 20 to 80% by weight in 100% by weight of polyisocyanate (B) having an average of 2.5 to 7 isocyanate groups in one molecule % Adhesive composition for laminated sheets containing a modified polyisocyanate (B ′) obtained by modifying% with a blocking agent (C).   The adhesive for laminated sheets according to claim 1, wherein the blocking agent (C) is at least one selected from the group consisting of ε-caprolactam, methyl ethyl ketone oxime, pyrazole compounds, malonic acid diesters, and acetylated ketone compounds. Agent composition.   The adhesive composition for laminated sheets according to claim 1 or 2, comprising 20 to 50 parts by weight of the epoxy resin (D) with respect to 100 parts by weight of the polyol (A).   The number average molecular weight of an epoxy resin (D) is 300-5,000, The adhesive composition for laminated sheets of Claim 3.   The adhesive composition for laminated sheets according to any one of claims 1 to 4, wherein the polyisocyanate (B) is at least one selected from a polyisocyanate derived from hexamethylene diisocyanate and a polyisocyanate derived from isophorone diisocyanate. .   The adhesive composition for laminated sheets according to any one of claims 1 to 5, comprising 0.1 to 5 parts by weight of the silane coupling agent (E) with respect to 100 parts by weight of the polyol (A).   The adhesive composition for laminated sheets according to any one of claims 1 to 6, wherein the isocyanate group concentration in the polyisocyanate (B) is 10 to 30% by weight.   The laminated body using the adhesive composition for laminated sheets in any one of Claims 1-7.   The solar cell back surface protection sheet using the adhesive composition for laminated sheets in any one of Claims 1-7.