JP2011105819A - Adhesive composition for laminated sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition that can form a strong and long-term durable adhesive bond between an untreated surface of a plastic film and other different substrates of a plastic, metal or the like, more specifically, can maintain adhesive strength over a long period of time by inhibiting the deterioration with time of an adhesive strength of a sheet formed by adhesively bonding an untreated surface of a plastic film with other different substrates during outdoor exposure. <P>SOLUTION: The adhesive composition for a laminated sheet includes (A) an acrylic polyol and (B) a polyisocyanate. In the adhesive composition, the acrylic polyol (A) has a number average molecular weight of 10,000 to 100,000, a hydroxyl value of 5 to 15 mgKOH/g and a glass transition temperature (Tg) of -40 to 10°C, and the equivalent ratio NCO/OH of an isocyanate group derived from the polyisocyanate (B) to a hydroxyl group derived from the acrylic polyol (A) is 3 to 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an adhesive composition for laminated sheets.

  In recent years, as a multilayer (composite) film used for outdoor industrial applications, for example, barrier materials, roofing materials, solar panel materials, window materials, outdoor flooring materials, lighting protection materials, automobile members, signboards, stickers, etc., aluminum or A laminated film made by bonding a metal foil or metal plate such as copper or steel plate or a metal vapor-deposited film and a plastic film such as polypropylene, polyvinyl chloride, polyester, fluororesin or acrylic resin has been used. It was. As an adhesive for laminating a metal foil, a metal plate, or a metal vapor-deposited film and a plastic film in these multilayer films, polyepoxy adhesives and polyurethane adhesives are known.

  Patent Document 1 discloses a polyester resin in consideration of balance, which can give excellent initial cohesive force and adhesive force, and a polyurethane resin adhesive using the polyester resin.

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

  Patent Document 3 discloses that a polyurethane adhesive 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, in recent years, efforts to combat global warming have become urgent. For materials such as solar cell backside sealing sheets and laminated sheets, it is required to develop and provide materials with long-term durability. To obtain long-term durability, several types of plastic films are laminated. There is a need to do. When laminating a plurality of plastic films, it is necessary to adhere a so-called untreated surface of the plastic film, on which the surface of the plastic film has not been subjected to treatment for improving the adhesive strength such as corona treatment.

  However, the above-mentioned conventional adhesives have a problem that the untreated surface of the plastic film and other base materials such as plastic and metal cannot be firmly bonded over a long period of time. Moreover, when bonding the untreated surfaces of the plastic film, it has been extremely difficult to achieve both sufficient initial adhesion and long-term durability.

JP-A-10-218978 JP-A-6-116542 JP 2008-4691 A JP 2007-136911 A

  INDUSTRIAL APPLICABILITY The present invention is capable of strongly and long-time bonding an untreated surface of a plastic film and another substrate such as plastic or metal, and more specifically, an outdoor sheet of a sheet obtained by bonding an untreated surface of a plastic film to another substrate. It is an object of the present invention to provide an adhesive that can suppress a decrease in adhesive strength over time during exposure 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 problems can be solved by the following adhesive composition for laminated sheets, and have completed the present invention. That is, the present invention
An adhesive composition for a laminated sheet comprising an acrylic polyol (A) and a polyisocyanate (B),
The number average molecular weight of the acrylic polyol (A) is 10,000 to 100,000, the hydroxyl value is 5 to 15 mgKOH / g, and the glass transition temperature (Tg) is −40 to 10 ° C. further,
The present invention relates to an adhesive composition for laminated sheets, wherein an equivalent ratio NCO / OH between a hydroxyl group derived from an acrylic polyol (A) and an isocyanate group derived from a polyisocyanate (B) is 3 to 10.

  Moreover, this invention relates to the adhesive composition for laminated sheets characterized by including 5-20 weight part of polycarbonate polyol and / or polycarbonate urethane polyol with respect to 100 weight part of acrylic polyol (A).

  The present invention also relates to the above adhesive composition for laminated sheets, wherein the acrylic polyol (A) has a structure that is at least partially chemically bonded to the polycarbonate polyol and / or the polycarbonate urethane polyol.

  Moreover, this invention relates to the said adhesive composition for laminated sheets characterized by using polyisocyanate (B) combining the polyisocyanate from which reaction rate differs.

  The present invention also relates to the above adhesive composition for laminated sheets, wherein the polyisocyanate (B) contains a polyisocyanate derived from isophorone diisocyanate.

  The present invention also relates to the above adhesive composition for laminated sheets, wherein the polyisocyanate (B) contains a polyisocyanate derived from trimethylxylene diisocyanate.

  The present invention also relates to the above adhesive composition for laminated sheets, wherein the polyisocyanate (B) contains a blocked isocyanate (B ′).

  The present invention also relates to the above adhesive composition for laminated sheets, wherein 0.1 to 5 parts by weight of the silane coupling agent (C) is contained with respect to 100 parts by weight of the acrylic polyol (A).

Moreover, this invention relates to the laminated body using the said adhesive composition for laminated sheets.

  By using the adhesive composition for laminated sheets of the present invention as an adhesive for laminated sheets, the untreated surface of the plastic film and other substrates such as plastic and metal can be bonded firmly and over a long period of time. Can provide an adhesive capable of maintaining the adhesive strength over a long period of time by suppressing a decrease in the adhesive strength with time during outdoor exposure of a sheet in which the untreated surface of the plastic film is adhered to another substrate.

<Acrylic polyol (A)>
As the acrylic polyol (A), a copolymer of a hydroxyl group-containing mono (meth) acrylate monomer and a mono (meth) acrylate monomer not containing a hydroxyl group is preferably used. The hydroxyl group-containing mono (meth) acrylate monomer is a monomer containing one (meth) acryloyl group and one or more hydroxyl groups in one molecule, which is a mono (meth) acrylate monomer of a dihydric alcohol, ε -Caprolactone modified (meth) acrylic monomers and the like are included.

  Examples of mono (meth) acrylic acid ester monomers of dihydric alcohol include, for example, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 1,4-butanediol mono (meth) acrylate, (poly) Examples include ethylene glycol mono (meth) acrylate.

  Furthermore, mono (meth) acrylic acid ester monomers of trivalent or higher alcohols such as 2,3-dihydroxypropyl (meth) acrylic acid can also be used as hydroxyl-containing mono (meth) acrylate monomers.

  As the mono (meth) acrylate monomer not containing a hydroxyl group, conventionally known radical polymerizable monomers can be appropriately selected and used. For example, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert- Representative of alkyl (meth) acrylate monomers such as butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, etc. Long chain (meth) acrylic monomers, acrylonitrile, and the like. Furthermore, carboxyl group-containing monomers such as (meth) acrylic acid, maleic acid, and maleic anhydride or anhydrides thereof, and vinyl monomers such as styrene can be used.

  In the present invention, the number average molecular weight of the acrylic polyol (A) needs to be 10,000 to 100,000. Furthermore, 30,000-80,000 is preferable. If it is less than 10,000, the heat-and-moisture resistance and the initial cohesive force are low, resulting in delamination and the like. On the other hand, when it exceeds 100,000, the viscosity of the adhesive is increased, which causes a problem in coatability.

  In addition, the number average molecular weight in this invention is a value of polystyrene conversion by gel permeation chromatography (GPC).

  The hydroxyl value of the acrylic polyol (A) is determined by the content of the hydroxyl group-containing mono (meth) acrylate monomer. In the present invention, the hydroxyl value needs to be 5 to 15 mgKOH / g. Furthermore, 5-14 mgKOH / g is more preferable. If it is less than 5 mgKOH / g, the crosslinking with the isocyanate curing agent is not sufficient, and the heat and humidity resistance is lowered. On the other hand, if it exceeds 15 mgKOH / g, the crosslink density becomes too high, and the adhesive strength of a difficult-to-adhere base material such as untreated PET is lowered. Here, “PET” is an abbreviation for “polyethylene terephthalate”.

  Moreover, in this invention, the glass transition point (Tg) of acrylic polyol (A) needs to be -40 degreeC-10 degreeC. Furthermore, -40 degreeC-5 degreeC is more preferable. If it is less than -40 degreeC, cohesion force will fall and it will float immediately after a lamination. In addition, the heat and humidity resistance is reduced. On the other hand, when the temperature is higher than 10 ° C., the adhesive strength to a hardly adhesive film such as untreated PET is lowered.

  Moreover, it is preferable that an acrylic polyol (A) contains a polycarbonate polyol and / or a polycarbonate urethane polyol from a viewpoint of adhesiveness, durability, and workability | operativity.

  The polycarbonate polyol has a number average molecular weight of 1,000 to 3,000, and 1,6-hexanediol, 3-methylpentanediol, etc. are used as the glycol component. These glycol components can be used alone or in combination. good. For example, as a commercial item, Ube Industries, Ltd. ETERNACOLL UH-100, 200, 300, Kuraray Kuraray polyol, C-2050, 2090, 3090 etc. are mentioned, Among these, one sort or two sorts or more are used. be able to.

  As the polycarbonate urethane polyol, a polycarbonate diol having a number average molecular weight of 5,000 to 20,000 and a terminal hydroxyl group can be used by extending the chain with a diisocyanate. Examples thereof include polycarbonate urethane polyol obtained by reacting Kuraray polyol C-2050, which is a polycarbonate diol, with isophorone diisocyanate, hexamethylene diisocyanate, which are diisocyanates, and the like.

  Moreover, it is also one of the preferable forms that a part of acrylic polyol (A) has a structure chemically bonded to polycarbonate polyol and / or polycarbonate urethane polyol. As a method for introducing the structure of polycarbonate polyol and / or polycarbonate urethane polyol into acrylic polyol (A), for example, the terminal hydroxyl group of polycarbonate polyol or polycarbonate urethane polyol, (meth) acryloyl group and isocyanate group Can be obtained by synthesizing an acrylic macromer having a radically polymerizable (meth) acryloyl group at one end by reacting with a monomer having the same in the same molecule, and then subjecting it to a radical polymerization reaction with the acrylic monomer. Examples of the monomer having a (meth) acryloyl group and an isocyanate group in the same molecule include Karenz MOI and AOI (manufactured by Showa Denko). Reacting an isocyanate group derived from a monomer having a (meth) acryloyl group and an isocyanate group in the same molecule with respect to 1 equivalent of a terminal hydroxyl group derived from a polycarbonate polyol or a polycarbonate urethane polyol, by ½ equivalent or less. Is preferred.

  5-20 weight part is preferable with respect to 100 weight part of acrylic polyol (A), and, as for content of polycarbonate polyol and / or polycarbonate urethane polyol, 5-15 weight part is more preferable. If the content exceeds 20 parts by weight, gelation tends to occur during the reaction.

<Polyisocyanate (B)>
The polyisocyanate (B) is a compound derived from a known diisocyanate, although not limited thereto. For example, 2,4-tolylene diisocyanate (alias: 2,4-TDI), 2,6-tolylene diisocyanate (alias: 2,6-TDI), xylylene diisocyanate (alias: XDI), diphenylmethane diisocyanate (alias: MDI), isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate (also known as HDI), bis (4-isocyanatocyclohexyl) methane, or hydrogenated diphenylmethane diisocyanate. Nurate, trimethylolpropane adduct, biuret type, prepolymer having isocyanate residue (low polymer obtained from diisocyanate and polyol), having isocyanate residue Uretdione body that, allophanate body, or their composites, and block isocyanate and the like, can be used in combination with either alone, or two or more.

  Moreover, it is preferable to use polyisocyanate (B) combining the polyisocyanate from which reaction rate differs from a heat-and-heat-resistant viewpoint. More specifically, it is preferable to use a combination of a polyisocyanate having a high reaction rate and a polyisocyanate having a low reaction rate. The polyisocyanate having a high reaction rate reacts with the acrylic polyol (A) in the low temperature aging process, and the polyisocyanate having a low reaction rate gradually reacts with moisture in the air during exposure to form a sea-island structure. Thereby, since the crosslinking density of acrylic polyol (A) and polyisocyanate (B) does not change over a long period from the initial stage, the heat and moisture resistance is improved.

  Examples of the polyisocyanate having a high reaction rate herein include at least one polyisocyanate selected from polyisocyanates derived from MDI, TDI, XDI, HDI, and the like. Examples thereof include at least one polyisocyanate selected from polyisocyanate derived from isophorone diisocyanate, polyisocyanate derived from trimethylxylene diisocyanate, and blocked isocyanate (B ′).

Examples of the combination of a polyisocyanate having a high reaction rate and a polyisocyanate having a low reaction rate include, for example, a combination of a polyisocyanate derived from HDI and a polyisocyanate derived from isophorone diisocyanate, or a derivative derived from HDI. A combination of a polyisocyanate and a polyisocyanate derived from trimethylxylene diisocyanate is preferred from the viewpoint of adhesive strength,
A combination of a polyisocyanate derived from HDI and a polyisocyanate derived from isophorone diisocyanate is more preferred from the viewpoint of yellowing.

  Further, the polyisocyanate (B) preferably contains a blocked isocyanate (B ′). Block isocyanate (B ′), for example, in the process of creating a solar cell backsheet, when the backsheet and the EVA as a base material are thermocompression bonded at a high temperature, it partially reacts with active hydrogen on the surface of the base material, The effect which improves adhesiveness with a base material can be anticipated.

  The blocked isocyanate (B ′) is a compound in which a part of the isocyanate group in the polyisocyanate (B) is modified with a blocking agent. Examples of the blocking agent include ε-caprolactam, methyl ethyl ketone oxime, and pyrazole. It is preferable to use at least one compound selected from the group consisting of a series compound, a malonic acid diester, and an acetylated ketone compound, but is not limited to these, and reacts with polyisocyanate (B). And after that, what deviates by heat processing can be used.

  The number of isocyanate groups in the polyisocyanate (B) is preferably 2.5 to 7 on average per molecule, and more preferably 2.7 to 3.7. When the number is less than 2.5, a sufficient amount of crosslinking cannot be obtained to obtain cohesive strength as an adhesive, and as a result, sufficient adhesive strength and long-term durability may not be obtained. When the number is more than 7, the crosslinking density of the adhesive is increased, and the adhesion during lamination may be lowered. Also, the pot life may be shortened, 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.

  The amount of the polyisocyanate (B) used is determined by the NCO / OH equivalent ratio of the hydroxyl group derived from the acrylic polyol (A) and the isocyanate group derived from the polyisocyanate (B). It is necessary to be 3-10, and it is more preferable that it is 3-9. If it is less than 3, the adhesive strength after indoor / outdoor exposure decreases. On the other hand, if it exceeds 10, the initial adhesive strength is lowered.

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

Examples of the silane coupling agent (C) 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 (C) 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 acrylic polyol (A). If it is less than 0.1 parts 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 in excess of 5 parts by weight, no further improvement in performance may be observed. is there.

  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 an acrylic polyol (A), a silane coupling agent (C), an organic solvent, and other additives, and the curing agent contains a polyisocyanate (B), an organic solvent, and other additives.

  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.

  Moreover, the adhesive composition of the present invention is preferably used as an adhesive for producing a solar cell back surface protective sheet, and can also be used as an anchor coating agent for a solar cell laminate sheet. 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 polyisocyanate (B), any known oxazoline compound such as 2,5-dimethyl-2-oxazoline or 2,2 may be used as long as the effects of the present invention are not impaired. -(1,4-butylene) -bis (2-oxazoline) or a hydrazide compound such as isophthalic acid dihydrazide, sebacic acid dihydrazide, or adipic acid dihydrazide may be included.

  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 multilayer film using the adhesive composition according to the present invention, a commonly used method can be employed. For example, after applying the adhesive composition to one side of one plastic film with a comma coater or dry laminator, volatilizing the solvent, pasting with the other laminate substrate, and curing at room temperature or under heating good. 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 (polyethylene naphthalate) film, fluorine-based film, It is preferable to apply and use it on a substrate or film surface that is extremely difficult to bond with a general adhesive composition such as an olefin substrate such as polypropylene.

  Hereinafter, the present invention will be described more specifically with reference to examples. In the examples, “parts” represents “parts by weight” and “%” represents “% by weight”.

<Production of acrylic polyol (A)>
Synthesis example 1
A 4-necked flask equipped with a condenser, a nitrogen inlet tube, a dropping funnel, and a thermometer was charged with 100 parts by weight of ethyl acetate, heated to 80 ° C., 68 parts by weight of butyl acrylate, 20 parts by weight of ethyl methacrylate, 10 parts of styrene. A monomer solution in which 2 parts by weight, 2 parts by weight of 2-hydroxyethyl acrylate, and 0.1 part by weight of azobisisobutylnitrile have been mixed in advance is dropped from a dropping funnel over 2 hours. Thereafter, a step of reacting for 1 hour and adding 0.1 part by weight of azobisisobutylnitrile and further reacting for 1 hour is performed until the monomer conversion reaches 98% or more, cooling, and further adding ethyl acetate. A 50% solids solution was obtained. Further, synthesis examples 2,3,4,5,6,7,8,10,11,12, shown in Table 1 were similarly performed except that the molecular weight was adjusted by the addition amount of the polymerization initiator azobisisobutylnitrile. Acrylic polyols of 13, 14, and 15 were obtained.

Synthesis Example 9
In a four-necked flask equipped with a condenser, a nitrogen introducing tube, a dropping funnel, and a thermometer, 68.8 parts by weight of butyl acrylate, 20 parts by weight of ethyl methacrylate, 1.2 parts by weight of 4-hydroxybutyl acrylate, polycarbonate diol [ 10 parts by weight of an acrylic macromer obtained by reacting 1 mol of acryloyloxyethyl isocyanate [manufactured by Showa Denko KK, Karenz AOI] with 1 mol of Kuraray Co., Ltd., Kuraray polyol C-2050], and a polymerization initiator block builder [ Aquema Co., Ltd., Block Builder MA] is mixed with 0.4 part by weight, heated to 80 ° C. and reacted for 2 hours. Thereafter, 25 parts by weight of toluene is added, and the temperature is raised to 110 ° C. for reaction. The reaction was carried out until the monomer conversion reached 95%, the mixture was cooled, and ethyl acetate was further added to obtain a 50% solid solution.

<Composition example of adhesive composition>
Examples 1-12, Comparative Examples 1-9
100 parts by weight of the acrylic polyol (A) as the main ingredient, 3 parts by weight of the polyisocyanate (B) as the curing agent, and 3 parts by weight of the silane coupling agent are blended as shown in Table 2, and further ethyl acetate The solid content was adjusted to 30%.

<Example of making laminated film>
Using the adhesive compositions of Examples and Comparative Examples, the adhesive composition was dried on an untreated surface of a polyester film [manufactured by Toray Industries, Inc., Lumirror X-10S, thickness 50 μm]: 4 to 5 g After being applied with a dry laminator in an amount of / m ² and volatilizing the solvent, it was laminated on an untreated surface of a polyester film [manufactured by Toray Industries, Inc., Lumirror X-10S, thickness 50 μm]. Thereafter, curing (aging) at 40 ° C. for 3 days was performed to cure the adhesive, and a laminated film was produced.

  In Tables 1 and 2, the combinations of the main agent and the curing agent in Examples 1 to 12 and Comparative Examples 1 to 9, and the initial adhesive strength of the laminated film and 1000 hours under an atmosphere of 85 ° C.-85% RH, 2000 hours, And the adhesion after 3000 hours exposure. A specific evaluation method will be described below.

<Initial adhesive strength>
The laminated film was cut into a size of 200 mm × 15 mm, and a T-type peel test was performed at a load rate of 300 mm / min using a tensile tester in accordance with the test method of ASTM D1876-61. The peel strength (N / 15 mm width) between the untreated polyester film surfaces was shown as an average value of five test pieces.

<Exposure test>
The laminated film was placed in a constant temperature and humidity chamber of 85 ° C.-85% RH and aged for 1000 hours, 2000 hours, and 3000 hours, and a moisture and heat resistance test was assumed assuming outdoor exposure. The laminated film aged was cut into a size of 200 mm × 15 mm, dried at room temperature for 6 hours, and then the adhesive strength was measured by the same method as the initial adhesive strength.

The evaluation is as follows.
Practical range: 3 N / 15 mm or more, and the adhesive does not cause cohesive failure.
Not practical: Less than 3 N / 15 mm or cohesive failure of the adhesive.
Even if the adhesive force is 3 N / 15 mm or more, the material that causes cohesive failure is a problem because the substrates bonded together at the time of processing are peeled off or the substrates are displaced.

  In Table 1, “Mn” represents the number average molecular weight, and “OH value” represents the hydroxyl value (unit: mgKOH / g). The unit of glass transition temperature (Tg) is “° C.”.

  As shown in Table 2, the adhesive compositions of the examples were excellent in adhesive strength after exposure at the initial stage and under high temperature and high humidity, and were able to maintain the adhesive strength over a long period of time. Therefore, it is considered that the adhesive compositions of these examples are excellent in long-term wet heat resistance for outdoor use.

  In addition, in JIS C 8917 (environmental test method and durability test method for crystal-based solar cell module), a moisture resistance test B-2 that is durable for 1000 hours at 85 ° C. and 85% RH is defined. It is known as a particularly severe test method. This test shows that the adhesive strength can be maintained over a long period of more than 1000 hours and 3000 hours, and it can be said that the adhesive composition of the present invention has sufficient long-term wet heat resistance.

  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)

An adhesive composition for a laminated sheet comprising an acrylic polyol (A) and a polyisocyanate (B),
The number average molecular weight of the acrylic polyol (A) is 10,000 to 100,000, the hydroxyl value is 5 to 15 mgKOH / g, and the glass transition temperature (Tg) is −40 to 10 ° C. further,
An adhesive composition for laminated sheets, wherein the equivalent ratio NCO / OH between the hydroxyl group derived from the acrylic polyol (A) and the isocyanate group derived from the polyisocyanate (B) is 3 to 10.   The adhesive composition for laminated sheets according to claim 1, comprising 5 to 20 parts by weight of a polycarbonate polyol and / or a polycarbonate urethane polyol with respect to 100 parts by weight of the acrylic polyol (A).   The adhesive composition for laminated sheets according to claim 2, wherein the acrylic polyol (A) has a structure in which at least a part of the acrylic polyol (A) is chemically bonded to the polycarbonate polyol and / or the polycarbonate urethane polyol.   The polyisocyanate (B) is used in combination with polyisocyanates having different reaction rates, and the adhesive composition for laminated sheets according to any one of claims 1 to 3.   The polyisocyanate (B) contains a polyisocyanate derived from isophorone diisocyanate, and the adhesive composition for laminated sheets according to any one of claims 1 to 4.   The polyisocyanate (B) contains a polyisocyanate derived from trimethylxylene diisocyanate, and the adhesive composition for laminated sheets according to any one of claims 1 to 5.   The adhesive composition for laminated sheets according to any one of claims 1 to 6, wherein the polyisocyanate (B) contains a blocked isocyanate (B ').   The adhesive composition for laminated sheets according to any one of claims 1 to 7, comprising 0.1 to 5 parts by weight of the silane coupling agent (C) with respect to 100 parts by weight of the acrylic polyol (A). .   The laminated body using the adhesive composition for laminated sheets in any one of Claims 1-8.