WO2013180252A1

WO2013180252A1 - Adhesive for laminated sheets

Info

Publication number: WO2013180252A1
Application number: PCT/JP2013/065123
Authority: WO
Inventors: Yasushi Yamada; Noriyoshi KAMAI; Shoko Ito; Hitoshi Ikeda
Original assignee: Henkel Japan Ltd.
Priority date: 2012-05-28
Filing date: 2013-05-24
Publication date: 2013-12-05
Also published as: TW201402749A; JP6001331B2; JP2013245313A

Abstract

An object of the present invention is to provide an adhesive for laminated sheets, which is excellent in initial adhesion to a film and is also excellent in long-term hydrolysis resistance at high temperature; a laminated sheet obtainable by using the adhesive; and an outdoor material obtainable by using the laminated sheet. Disclosed is an adhesive for laminated sheets, comprising a urethane resin obtainable by mixing an acrylic polyol with an isocyanate compound, and a silane compound, wherein the acrylic polyol is obtainable by polymerizing a polymerizable monomer, the polymerizable monomer contains a monomer having a hydroxyl group and the other monomer, and the other monomer contains acrylonitrile. The adhesive for laminated sheets is excellent in initial adhesion to a film and is also excellent in long-term hydrolysis resistance at high temperature. The adhesive is preferably used for outdoor materials, and is particularly useful as an adhesive for solar battery back sheets.

Description

DESCRIPTION

ADHESIVE FOR LAMINATED SHEETS

Cross-Reference to Related Application

[0001]

This application claims priority under Article 4 of the Paris Convention based on Japanese Patent Application No. 2012-120921 filed on May 28, 2012 in Japan, the entire content of which is incorporated herein by reference.

Technical Field

[0002]

The present invention relates to an adhesive for laminated sheets. The present invention also relates to a laminated sheet obtainable by using the adhesive, and an outdoor material obtainable by using the laminated sheet.

Background Art

[0003]

Outdoor materials such as wall protecting materials, roofing materials, solar battery panel materials, window materials, outdoor flooring materials, illumination protection materials, automobile members, and signboards comprise, as a constituent material, a laminate (or a laminated sheet) obtained by laminating a plurality of films with each other using an adhesive. Examples of the film of which the laminate is composed include metal foils made of metals such as aluminum, copper, and steel; metal plates and metal deposited films; and films made of plastics such as polypropylene, polyvinyl chloride, polyester, fluororesin, and acrylic resin.

[0004]

As shown in Fig. 1, a laminated sheet 10 is a laminate of a plurality of films 11 and 12, and the films 11 and 12 are laminated by interposing an adhesive 13 therebetween.

Since the laminate is exposed outdoors over a long term, excellent durability is required of an adhesive for laminated sheets. It is required for adhesives for

laminated sheets, particularly adhesives for solar battery applications which convert sunlight into electricity, to have a higher level of durability than that of a

conventional adhesive.

[0005]

As shown in Fig. 3, in the case of solar battery applications, the laminated sheet 10 referred to as a back sheet is included in a solar battery module 1, together with a sealing material 20, a solar battery cell 30, and a glass plate 40.

Since the solar battery module 1 is exposed outdoors over a long term, sufficient durability against sunlight is required under conditions of high temperature and high humidity. Particularly, when the adhesive 13 has poor performance, the film 11 and the . film 12 are peeled, and thus the appearance of the sheet 10 deteriorates.

Therefore, it is required that the adhesive for laminated sheets for the production of the solar battery module does not undergo peeling of the film even if the adhesive is exposed to a high temperature over a long term.

[0006]

Patent Documents 1 to 3 disclose, as examples of adhesives for laminated sheets, urethane based adhesives for the production of a solar battery protection sheet.

Patent Document 1 discloses that a urethane adhesive for laminated sheets synthesized from an acrylic polyol is suited as an adhesive for solar battery back sheets (see Patent Document 1, Claim 1 and [0048] ) .

Patent Document 2 discloses a protective sheet for solar battery modules in which an acrylic urethane resin is formed on a base material sheet (see Patent Document 2, Claim 1, and Figs. 1 to 3) .

Patent Document 3 describes mixing an isocyanate curing agent with an acrylic polyol to produce adhesives (see Patent Document 3, Table 1, Table 2); a solar battery back sheet is produced by using these adhesives (see Patent Document 3 , [0107] ) . [0007]

Patent Documents 1 to 3 teach that poor appearance of a solar battery module can be prevented by producing a solar battery back sheet using an adhesive which is

excellent in hydrolysis resistance and laminate strength. However, the durability required of an adhesive for solar battery back sheets has been increasing year by year, and it is hard to say that the adhesives of these documents meet the high requirements of consumers .

The solar battery back sheet is commonly produced by applying an adhesive having a moderate viscosity on a film, drying the adhesive, laminating a film (dry lamination method) , and aging the laminate for several days .

Therefore, it is also required for the adhesive for solar battery back sheets to have excellent initial adhesion to a film in the lamination.

[0008]

Since the solar battery module is used outdoors under conditions of high temperature and high humidity, plural films composing the back sheet (laminated sheet) are likely to be peeled. In particular, it is difficult for a

fluororesin based film to bond to other various base materials using the adhesive. When the back sheet is exposed outdoors over a long term, adhesive strength between the adhesive and the fluororesin based film may drastically decrease. It is required for the adhesive for solar battery back sheets to have hydrolysis resistance and initial adhesion in a higher level. The use of adhesive for bonding fluororesin based films leads to an urgent need to suppress deterioration of adhesion of the adhesive.

[0009]

Patent Document 1: JP 2011-105819 A

Patent Document 2: JP 2010-238815 A

Patent Document 3: JP 2010-263193 A

Disclosure of the Invention

Problems to be Solved by the Invention

[0010]

The present invention has been made so as to solve such a problem and an object thereof is to provide an adhesive for laminated sheets which is excellent in initial adhesion to a film in the production of a laminate

(laminated sheet) using a fluororesin based film or a polyolefin based film and is also excellent in long-term hydrolysis resistance at high temperature; a laminated sheet obtainable by using the adhesive; and an outdoor material obtainable by using the laminated sheet.

Means for Solving the Problems

[0011] The present inventors have intensively studied and found, surprisingly, that it is possible to obtain an adhesive for laminated sheets, which is excellent in initial adhesion to a film and long-term hydrolysis resistance at high temperature, when a specific polyol is used as a raw material of a urethane resin and also a silane compound is added as a coupling agent, and thus completing the present invention.

[0012]

Namely, the present invention provides, in an aspect, an adhesive for laminated sheets, comprising a urethane resin obtainable by mixing an acrylic polyol with an isocyanate compound; and a silane compound, wherein the acrylic polyol is obtainable by polymerizing a

polymerizable monomer; the polymerizable monomer contains a monomer having a hydroxyl group and the other monomer; and the other monomer contains acrylonitrile .

[0013]

The present invention provides, as an embodiment, the adhesive for laminated sheets, wherein the isocyanate compound comprises at least one selected from a

trimethylolpropane adduct form, an isocyanurate form, a biuret form, an allophanate form and a monomer of an isocyanate .

The present invention provides, as an embodiment, the adhesive for laminated sheets, wherein the acrylic polyol has a glass transition temperature (Tg) of from -20 °C to 20°C.

[0014]

The present invention provides, in another aspect, a laminated sheet obtainable by using the above defined adhesive .

The present invention provides, in a preferred aspect, an outdoor material obtainable by using the laminated sheet.

[0015]

The present invention provides, in still another aspect, a raw material comprising an acrylic polyol for producing the above adhesive for laminated sheets, wherein the acrylic polyol is obtainable by polymerizing a

Effects of the Invention

[0016]

The adhesive for laminated sheets according to the present invention comprises a urethane resin obtainable by mixing an acrylic polyol with an isocyanate compound; and a silane compound, wherein the acrylic polyol is obtainable b polymerizing a monomer having a hydroxyl group and at least one other monomer; wherein the at least one other monomer contains acrylonitrile . Therefore, the adhesive for laminated sheets is excellent in initial adhesion to a film and in long-term hydrolysis resistance at high

temperature. This adhesive is preferably used for outdoor materials, and is particularly useful as an adhesive for solar battery back sheets .

[0017]

In the adhesive for laminated sheets according to the present invention, when the isocyanate compound comprises at least one selected from a trimethylolpropane adduct form, an isocyanurate form, a biuret from, an allophanate form and a monomer of an isocyanate, the hydrolysis resistance of the adhesive is remarkably improved, and thus the

adhesive is able to withstand use over a long term at high temperature and high humidity.

In the adhesive for laminated sheets according to the present invention, when the acrylic polyol has a glass transition temperature (Tg) of from -20 °C to 20 °C, the initial adhesion to a film is further improved while

maintaining hydrolysis resistance.

[0018]

The laminated sheet according to the present invention is obtainable by using the above adhesive for laminated sheets, and is therefore more excellent in productivity. and can also prevent peeling of the film, from the adhesive when the laminated sheet is exposed outdoors for a long period from the beginning of lamination. Even when a fluororesin based film having poor adhesion to various base materials is used, it is possible to maintain the above- mentioned initial adhesion and hydrolysis resistance at high temperature .

The outdoor material according to the present

invention is obtainable by using the above laminated sheet, and is therefore excellent in productivity, and is also less likely to exhibit poor appearance and is also more excellent in durability.

[0019]

In the raw material comprising an acrylic polyol for producing the adhesive for laminated sheets according to the present invention, the acrylic polyol is obtainable by polymerizing a monomer having a hydroxyl group and at least one other monomer; the at least one other monomer contains acrylonitrile . Therefore, a urethane resin having

excellent initial adhesion and long-term hydrolysis

resistance at high temperature is produced by reacting said raw material with an isocyanate compound, and thereby it is possible to provide an adhesive suited for outdoor material applications, and particularly an adhesive for laminated sheets, which is useful as an adhesive for solar battery back sheets.

Brief Description of the Drawings

[0020]

Fig. 1 is a sectional view of an embodiment of the laminated sheet of the present invention.

Fig. 2 is a sectional view of another embodiment of the laminated sheet of the present invention.

Fig. 3 is a sectional view of an embodiment of the outdoor material (for example, a solar battery module) of the present invention.

Embodiments for Carrying Out the Invention

[0021]

The adhesive for laminated sheets according to the present invention includes a urethane resin obtainable by mixing an acrylic polyol with an isocyanate compound, and a silane compound.

The urethane resin is a polymer obtainable by mixing and reacting the acrylic polyol with the isocyanate

compound, and has a urethane bond. A hydroxyl group of the acrylic polyol reacts with an isocyanate group.

The acrylic polyol is obtainable by the addition polymerization of polymerizable monomer, and the

polymerizable monomer includes a "monomer having a hydroxyl group" and the "other monomer" .

[0022]

The "monomer having a hydroxyl group" is a radical polymerizable monomer having a hydroxyl group and an ethylenic double bond, and is not particularly limited as long as the objective adhesive for laminated sheets of the present invention can be obtained. The monomer having a hydroxyl group includes for example, hydroxyalkyl

(meth) acrylate , and the hydroxyalkyl (meth) acrylate may be used alone, or two or more hydroxyalkyl (meth) acrylates may be used in combination. The hydroxyalkyl (meth) acrylate may also be used in combination with a monomer having a hydroxyl group, other than the hydroxyalkyl (meth) acrylate .

[0023]

Examples of the "hydroxyalkyl (meth) acrylate" include, but are not limited to, 2 -hydroxyethyl (meth) acrylate , 2- hydroxypropyl (meth) acrylate , 3 -hydroxypropyl

(meth) acrylate, 4 -hydroxybutyl acrylate and the like.

Examples of the "polymerizable monomer having a hydroxyl group, other than the hydroxylalkyl

(meth) acrylate" include polyethylene glycol

mono (meth) acrylate , polypropylene glycol mono (meth) acrylate and the like.

[0024]

The "other monomer" is a "radical polymerizable monomer having an ethylenic double bond" other than the monomer having a hydroxyl group and contains acrylonitrile, and is not particularly limited as long as the objective adhesive of the present invention can be obtained. The other monomer may further include a (meth) acrylic ester. The other monomer may further include a radical

polymerizable monomer having an ethylenic double bond, other than acrylonitrile and (meth) acrylic ester.

[0025]

The " (meth) acrylic ester" is obtainable, for example, by the condensation reaction of (meth) acrylic acid with a monoalcohol, and has an ester bond. Even though it has an ester bond, a monomer having a hydroxyl group is not included in the (meth) acrylic ester. Specific examples thereof include (meth) acrylic acid alkyl esters such as methyl (meth) acrylate , ethyl (meth) acrylate , butyl

(meth) acrylate , 2-ethylhexyl (meth) acrylate , cyclohexyl (meth) acrylate , dicyclopentyl (meth) acrylate , and isobornyl (meth) acrylate ; glycidyl (meth) acrylate and the like. Both linear alkyl group and cyclic alkyl group are included in this "alkyl group".

[0026]

In the present invention, it is preferred to include at least one selected from methyl (meth) acrylate , ethyl (meth) acrylate , butyl (meth) acrylate , 2-ethylhexyl (meth) acrylate , and cyclohexyl (meth) acrylate , and it is more preferred to include at least one selected from methyl (meth) acrylate , ethyl (meth) acrylate , and butyl

(meth) acrylate .

[0027]

Examples of the "radical polymerizable monomers having an ethylenic double bond, other than acrylonitrile and (meth) acrylic ester" include, but are not limited to,

(meth) acrylic acid, styrene, vinyltoluene and the like.

The "acrylonitrile" is a compound represented by the chemical formula: CH₂ =CH-CN, and is also called acrylic nitrile, acrylic acid nitrile, or vinyl cyanide.

[0028]

The content of acrylonitrile is preferably from 1 to 40 parts by weight, more preferably from 5 to 35 parts by weight, and particularly preferably from 5 to 25 parts by weight, based on 100 parts by weight of the polymerizable monomers. When the content of the acrylonitrile is within the above range, it is possible to obtain an adhesive for solar battery back sheets, which exhibits an excellent balance among coatability, initial adhesion to a film, and adhesion (hydrolysis resistance) at high temperature.

In the present description, acrylic acid and

methacrylic acid are collectively referred to as

" (meth) acrylic acid", and "acrylic ester and methacrylic ester" are collectively referred to as " (meth) acrylic ester" or " (meth) acrylate" .

[0029]

As long as the objective adhesive for laminated sheets of the present invention can be obtained, there is no particular limitation on the polymerization method of the polymerizable monomers. For example, the above-mentioned polymerizable monomers can be radically polymerized by a conventional solution polymerization method in an organic solvent using an appropriate catalyst. Herein, there is no particular limitation on the organic solvent as long as it can be used so as to polymerize the polymerizable monomer, and it does not substantially exert an adverse influence on the properties of the adhesive after the polymerization reaction. Examples of such solvent include aromatic

solvents such as toluene and xylene; ester based solvents such as ethyl acetate and butyl acetate; and combinations thereof .

The polymerization reaction conditions such as

reaction temperature, reaction time, type of organic

solvents, type and concentration of monomers, stirring rate, as well as the type and concentration of polymerization initiators in the polymerization of the polymerizable monomers can be appropriately selected according to

characteristics and so on of the objective adhesive. [0030]

The "polymerization initiator" is preferably a

compound which can accelerate the polymerization of the polymerizable monomer by the addition in a small amount and can be used in an organic solvent . Examples of the

polymerization initiator include ammonium persulfate, t- butyl peroxybenzoate, 2 , 2 -azobisisobutyronitrile (AIBN) , and 2 , 2-azobis (2 , 4 -dimethylvarelonitrile) .

A chain transfer agent can be appropriately used for the polymerization in the present invention in order to adjust the molecular weight. It is possible to use, as the "chain transfer agent", compounds well-known to those skilled in the art. Examples thereof include mercaptans such as n-dodecylmercaptan (nDM) , laurylmethylmercaptan, and mercaptoethanol .

[0031]

As mentioned above, the acrylic polyol is obtainable by polymerizing the polymerizable monomer. From the viewpoint of coatability of the adhesive, the weight average molecular weight ( w) of the acrylic polyol is preferably 200,000 or less, and more preferably from 5,000 to 100,000. The weight average molecular weight (Mw) is a value measured by gel permeation chromatography (GPC) in terms of polystyrene standard. Specifically, the value can be measured using the following GPC apparatus and measuring method. HCL-8220GPC manufactured by TOSOH CORPORATION is used as a GPC apparatus, and RI is used as a detector. Two TSKgel SuperMultipore HZ-M manufactured by TOSOH

CORPORATION are used as a GPC column. A sample is

dissolved in tetrahydrofuran and the obtained solution is allowed to flow at a flow rate of 0.35 ml/minute and at a column temperature of 40 °C, and then Mw is determined by conversion of observed molecular weight based on a

calibration curve which is obtained by using polystyrene having a monodisperse molecular weight as a standard reference material.

[0032]

The glass transition temperature (Tg) of the acrylic polyol can be set by adjusting the mass fraction of a given monomer being used. The glass transition temperature (Tg) of the acrylic polyol can be determined based on a glass transition temperature of a homopolymer obtainable from each monomer and a mass fraction of the homopolymer used in the acrylic polyol using the following calculation formula (i) . It is preferred to determine a composition of the monomer using the glass transition temperature determined by the calculation:

(i) : 1/Tg = Wl/Tgl + W2/Tg2 + ^■ · · + Wn/Tgn

where Tg in the above formula (i) denotes the glass

transition temperature of the acrylic polyol, each of Wl, W2 , ^{■ ■ ■} , Wn denotes a mass fraction of each monomer, and each of Tgl, Tg2 , · · · , and Tgn denotes a glass transition temperature of a homopolymer of each corresponding monomer.

[0033]

A value disclosed in a document can be used as a Tg of the homopolymer. It is possible to refer, for example, to the following documents: Acrylic Ester Catalog of

Mitsubishi Rayon Co., Ltd. (1997 Version), edited by Kyozo Kitaoka; "Shin Kobunshi Bunko 7, Guide to Synthetic Resin for Coating Material", Kobunshi Kankokai, published in 1997, pp.168-169; and "POLYMER HANDBOOK", 3rd Edition, pp.209-277, John Wiley & Sons, Inc. published in 1989.

In the present specification, the glass transition temperatures of homopolymers of the following monomers are as follows.

Methyl methacrylate: 105 °C

n-Butyl acrylate : -54°C

Ethyl acrylate: -20°C

2 -Hydroxyethyl methacrylate: 55 °C

2 -Hydroxyethyl acrylate: -15°C

Glycidyl methacrylate: 41°C

Acrylonitrile : 130°C

Styrene: 105 °C

[0034]

In the present invention, the glass transition temperature of the acrylic polyol is preferably from -20 °C to 20°C, more preferably -15°C to 20°C, and particularly preferably -10°C to 15°C, from the viewpoint of the initial adhesion to a film. When the glass transition temperature of the acrylic polyol is within the above range, the adhesive of the present invention is less likely to

decrease in cohesive force, is more excellent in initial adhesion, and also can maintain hydrolysis resistance more satisfactorily.

[0035]

The hydroxyl value of the acrylic polyol is preferably from 0.5 to 45 mgKOH/g, more preferably from 1 to 40 mgKOH/g, and particularly preferably from 3 to 30 mgKOH/g. When the hydroxyl value of the acrylic polyol is within the above range, it is possible to obtain the adhesive which is improved in initial adhesion, adhesion at high temperature, and hydrolysis resistance. In particular, when a solar battery back sheet is produced by laminating a plurality of films using the adhesive of the present invention, the film becomes much less likely to peel from the adhesive.

In the present description, the hydroxyl value is a number of mg of potassium hydroxide required to neutralize acetic acid combined with hydroxyl groups when 1 g of a resin is acetylated.

In the present invention, the hydroxyl value is specifically calculated by the following formula (ii) .

(ii) : Hydroxyl value = [(weight of (meth) acrylate having a hydroxyl group) / (molecular weight of

(meth) acrylate having a hydroxyl group)] ^χ (mole number of hydroxyl groups contained in 1 mol of (meth) acrylate

monomer having a hydroxyl group) ^χ (formula weight of KOH ^χ 1 , 000) / (weight of the acrylic polyol)

[0036]

There is no particular limitation on the isocyanate compound according to the present invention as long as the objective adhesive of the present invention can be obtained, and is preferably at least one selected from a

trimethylolpropane adduct, an isocyanurate form, a buret form, an allophanate form, and an isocyanate monomer.

When the isocyanate compound contains these compounds, the adhesive for laminated sheets can be used more

preferably over a long term at high temperature and high humidity since the hydrolysis resistance is remarkably improved .

The isocyanate compound is mainly classified into an "isocyanate having no aromatic ring" and an "isocyanate having an aromatic ring". In addition, for example,

trimethylolpropane (TMP) is included in the polyhydric alcohols, but the polyhydric alcohol is not limited only to the TMP. [0037]

Examples of the isocyanate having no aromatic ring include an "aliphatic isocyanate" and an "alicyclic isocyanate" .

The aliphatic isocyanate refers to a compound which has a chain- like (or linear) hydrocarbon chain in which isocyanate groups are directly combined to the hydrocarbon chain, and also has no cyclic hydrocarbon chain.

The alicyclic isocyanate is a compound which has a cyclic hydrocarbon chain and may have a chain- like

hydrocarbon chain. The isocyanate group may be either directly combined with the cyclic hydrocarbon chain, or may be directly combined with the chain- like hydrocarbon chain which may be present .

[0038]

Examples of the aliphatic isocyanate include 1,4- diisocyanatobutane, 1, 5-diisocyanatopentane, 1,6- diisocyanatohexane (HDI) , 1 , 6-diisocyanato-2 , 2 , 4- trimethylhexane , methyl 2 , 6 -diisocyanatohexanoate (lysine diisocyanate) and the like.

Examples of the alicyclic isocyanate include 5- isocyanato- 1 - isocyanatomethyl- 1 , 3 , 3 -trimethylcyclohexane (isophorone diisocyanate), 1,3- bis (isocyanatomethyl) cyclohexane (hydrogenated xylylene diisocyanate) , bis (4 -isocyanatocyclohexyl ) methane (hydrogenated diphenylmethane diisocyanate) , 1,4- diisocyanatocyclohexane and the like.

[0039]

It is sufficient for the isocyanate having an aromatic ring (hereinafter referred to as an aromatic isocyanate) to have an aromatic ring, and it is not necessary that

isocyanate groups are directly combined with the aromatic ring. The aromatic ring may be an aromatic ring in which two or more benzene rings are fused.

Examples of the aromatic isocyanate include 4,4'- diphenylmethane diisocyanate (MDI) , p-phenylene

diisocyanate, m-phenylene diisocyanate, tolylene

diisocyanate (TDI) , xylene diisocyanate (XDI) and the like. These isocyanate compounds can be used alone or in

combination.

Since xylylene diisocyanate (OCN-CH₂ -C₆ H₄ -CH₂ -NCO) has an aromatic ring, it corresponds to the aromatic isocyanate even though the isocyanate groups are not directly combined with the aromatic ring.

[0040]

In the present invention, the isocyanate compound is particularly preferably HDI as the aliphatic isocyanate, isophorone diisocyanate as the alicyclic isocyanate, and 4 , 4 ' -diphenylmethane diisocyanate (MDI), tolylene

diisocyanate (TDI) and xylene diisocyanate (XDI) as the aromatic isocyanate, from the viewpoint of improving initial adhesion to a film after aging, curing time, and hydrolysis resistance.

Among these isocyanates, HDI is more preferably an isocyanurate form, isophorone diisocyanate is more

preferably an isocyanurate form, and TDI is more preferably an adduct form with trimethylolpropane .

[0041]

The urethane resin according to the present invention is obtainable by reacting the acrylic polyol with the isocyanate compound. In the reaction, a known method can be used and the reaction can be usually performed by mixing the acrylic polyol with the isocyanate compound. There is no particular limitation on the mixing method as long as the urethane resin according to the present invention can be obtained.

In the present invention, an equivalence ratio of the isocyanate group based on the isocyanate having an aromatic ring to the hydroxyl group based on the acrylic polyol is preferably 0.5 or more, more preferably from 0.5 to 2.5, and most preferably from 0.5 to 2.0. When the equivalence ratio is 0.5 or more, the adhesive is excellent in heat resistance and shows improved hydrolysis resistance at high temperature .

[0042] The adhesive for laminated sheets of the present invention contains a silane compound. It is possible to use, as the silane compound,

(meth) acryloxyalkyltrialkoxysilanes ,

(meth) acryloxyalkylalkylalkoxysilanes ,

vinyltrialkoxysilanes , vinylalkylalkoxysilanes ,

epoxysilanes , mercaptosilanes and isocyanurate silanes. However, the silane compound is not limited only to these silane compounds.

[0043]

Examples of the " (meth) acryloxyalkyltrialkoxysilanes' include 3 - (meth) acryloxypropyltrimethoxysilane , 3- (meth) acryloxypropyltriethoxysilane, 2- (meth) acryloxyethyltrimethoxysilane and the like.

Examples of the

" (meth) acryloxyalkylalkylalkoxysilanes" include 3- (meth) acryloxypropylmethyldimethoxysilane , 3 - (meth) acryloxypropylmethyldiethoxysilane , 3 - (meth) acryloxypropylethyldiethoxysilane and 2- (meth) acryloxyethylmethyldimethoxysilane .

[0044]

Examples of the "vinyltrialkoxysilanes" include vinyltrimethoxysilane , vinyltriethoxysilane ,

vinyldimethoxyethoxysilane, vinyltri (methoxyethoxy) silane, vinyltri (ethoxymethoxy) silane and the like. Examples of the "vinylalkylalkoxysilanes" include vinylmethyldimethoxysilane ,

vinylethyldi (methoxyethoxy) silane,

vinyldimethylmethoxysilane ,

vinyldiethyl (methoxyethoxy) silane and the like.

[0045]

For example, the "epoxysi lanes" can be classified into a glycidyl based silane compound and an epoxycyclohexyl based silane compound. The "glycidyl based silane" has a glycidoxy group, and specific examples thereof include 3- glycidoxypropylmethyldiisopropoxysilane , 3 - glycidoxypropyltrimethoxysilane , 3 - glycidoxypropyltriethoxysilane , 3 - glycidoxypropyldiethoxysilane and the like.

The "epoxycyclohexyl based silane" has a 3,4- epoxycyclohexyl group, and specific examples thereof include 2 - (3 , 4 -epoxycyclohexyl) ethyltrimethoxysilane , 2-

(3 , 4-epoxycyclohexyl) ethyltriethoxysilane and the like.

[0046]

Examples of the "mercaptosilanes" include 3- mercaptopropyltrimethoxysilane , 3 - mercaptopropyltriethoxysilane and the like. Examples of the "isocyanurate silanes" include tris(3-

(trimethoxysilyl) ropyl) isocyanurate and the like.

[0047] These silane compounds preferably act as a silane coupling agent. The silane coupling agent refers to a compound composed of an organic substance and silicon, and which compound also has both an organic functional group "Y" such as an amino group, an epoxy group, a methacrylic group, a vinyl group, or a mercapto group, which group is expected to react or interact with an organic substance, and a hydrolyzable group "OR" such as a methoxy group, an ethoxy group, or a methylcarbonyloxy group in one molecule, and which compound can combine an organic material and an inorganic material, while the organic material and the inorganic material are usually much less likely to be combined each other.

When the adhesive of the present invention contains a silane compound, initial adhesion and hydrolysis resistance are improved, and initial adhesion to a fluororesin such as polyvinylidene fluoride (PVDF) , a polyolefin such as polyethylene, and a polyester such as polyethylene

terephthalate (PET) is particularly excellent.

The silane compound may be mixed in advance with the acrylic polyol, or may be post-added to the urethane resin obtainable by mixing the acrylic polyol with the isocyanate compound .

[0048]

The silane compound may be contained in the adhesive for laminated sheets in a state of being combined with the urethane resin after reacting with the isocyanate compound, or may be contained in the adhesive for laminated sheets in an unreacted state.

In the present invention, the silane compound is preferably an epoxysilane compound, and particularly preferably a glycidyl based silane. The glycidyl based silane compound is most suitable for improving initial adhesion and hydrolysis resistance of the adhesive for laminated sheets.

[0049]

The adhesive of the present invention may contain an ultraviolet absorber for the purpose of improving long-term weatherability . It is possible to use, as the ultraviolet absorber, a hydroxyphenyltriazine based compound and other commercially available ultraviolet absorbers. The

"hydroxyphenyltriazine based compound" is one type of a triazine derivative in which a hydroxyphenyl derivative is combined with a carbon atom of the triazine derivative, and examples thereof include TINUVIN 400, TINUVIN 405, TINUVIN 479, TINUVIN 477 and TINUVIN 460 (all of which are trade names) which are available from BASF Corporation.

[0050]

The adhesive for laminated sheets may further contain a hindered phenol based compound. The "hindered phenol based compound" is commonly referred to as a hindered phenol based compound, and there is no particular

limitation as long as the objective adhesive according to the present invention can be obtained.

Commercially available products can be used as the hindered phenol based compound. The hindered phenol based compound is, for example, commercially available from BASF Corporation. Examples thereof include IRGANOX1010,

IRGANOX1035, IRGANOX1076, IRGANOX1135, IRGANOX1330 and IRGANOX1520 (all of which are trade names) . The hindered phenol based compound is added to the adhesive as an antioxidant and may be used, for example, in combination with a phosphite based antioxidant, a thioether based antioxidant, an amine based antioxidant and the like.

[0051]

The adhesive for laminated sheets according to the present invention may further contain a hindered amine based compound. The "hindered amine based compound" is commonly referred to as a hindered amine based compound, and there is no particular limitation as long as the objective adhesive according to the present invention can be obtained.

Commercially available products can be used as the hindered amine based compound. Examples of the hindered amine based compound include TINUVIN 765, TINUVIN 111FDL, TINUVIN 123, TINUVIN 144, TINUVIN 152, TINUVIN 292 and TINUVIN 5100 (all of which are trade names) which are commercially available from BASF Corporation. The hindered amine based compound is added to the adhesive as a light stabilizer and may be used, for example, in combination with a benzotriazole based compound, a benzoate based compound and the like.

[0052]

The adhesive for laminated sheets according to the present invention can further contain other components as long as the objective adhesive can be obtained.

There is no particular limitation on timing of the addition of the "other components" to the adhesive as long as the objective adhesive according to the present

invention can be obtained. For example, the other

components may be added, together with the acrylic polyol and the isocyanate compound, in the synthesis of the urethane resin, or may be added after synthesizing the urethane resin by reacting the acrylic polyol with the isocyanate compound.

[0053]

Examples of the "other component" include a tackifier resin, a pigment, a plasticizer, a flame retardant, a wax and the like.

Examples of the "tackifier resin" include a styrene based resin, a terpene based resin, aliphatic petroleum resin, an aromatic petroleum resin, a rosin ester, an acrylic resin, a polyester resin (excluding

polyesterpolyol) and the like.

Examples of the "pigment" include titanium oxide, carbon black and the like.

Examples of the "plasticizer" include dioctyl

phthalate, dibutyl phthalate, diisononyl adipate, dioctyl adipate, mineral spirit and the like.

Examples of the "flame retardant" include a halogen based flame retardant, a phosphorous based flame retardant, an antimony based flame retardant, a metal hydroxide based flame retardant and the like.

The "wax" is preferably a wax such as a paraffin wax and a microcrystalline wax.

[0054]

Viscosity of the adhesive for laminated sheets

according to the present invention is measured by using a rotational viscometer (Model BM, manufactured by TOKIMEC Inc.) . When solution viscosity at the solid content of 40% is 4,.000 mPa -s or more, coatability of the adhesive may deteriorate. If further solvent is added so as to

decrease the viscosity, coating is performed at low solid component concentration, and thus productivity of the adhesive for laminated sheets may deteriorate. [0055]

The adhesive for laminated sheets of the present invention can be produced by mixing the above-mentioned urethane resin and silane compound, and an ultraviolet absorber, an antioxidant, a light stabilizer and/or other components which can be optionally added. There is no particular limitation on the mixing method as long as the objective adhesive of the present invention can be obtained. There is also no particular limitation on the order of mixing the components . The adhesive according to the present invention can be produced without requiring a special mixing method and a special mixing order. The obtained adhesive can maintain excellent hydrolysis

resistance at high temperature over a long term, and is also excellent in initial adhesion to a film.

Therefore, a laminated sheet is produced by laminating a plurality of adherends using the adhesive for laminated sheets of the present invention, and the obtained laminated sheet is used for the production of various outdoor

materials.

[0056]

Examples of the outdoor material of the present

invention include wall protecting materials, roofing

materials, solar battery modules, window materials, outdoor flooring materials, illumination protection materials, automobile members, and signboards. These outdoor

materials include, as an adherend, a laminated sheet

obtained by laminating a plurality of films with each other. Examples of the film include a film obtained by depositing metal on a plastic film (metal deposited film) and a film with no metal deposited thereon (plastic film) .

It is required for an adhesive for producing solar battery modules, among the adhesive for laminated sheets, to have a particularly high level of initial adhesion to a film after aging and of curing rate, and further have long- term hydrolysis resistance at high temperature. The

adhesive for laminated sheets of the present invention is excellent in long-term hydrolysis resistance at high

temperature, and thus the adhesive is suitable as an

adhesive for solar battery back sheets.

[0057]

In the case of producing a solar battery back sheet, the adhesive of the present invention is applied to a film. 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 methods. Plural films coated with the urethane adhesive of the present invention are laminated with each other to complete the solar battery back sheet .

An embodiment of the solar battery back sheet of the present invention is shown in each of Figs. 1 to 3 , but the present invention is not limited to these embodiments.

[0058]

Fig. 1 is a sectional view of a solar battery back sheet as an embodiment of laminated sheets of the present invention. The solar battery back sheet 10 is formed of two films and an adhesive for laminated sheets 13

interposed therebetween, and the two films 11 and 12 are laminated each other using the adhesive for laminated sheets 13. The films 11 and 12 may be made of either the same or different material. In Fig. 1, the two films 11 and 12 are laminated each other, or three or more films may be laminated one another.

[0059]

Another embodiment of the laminated sheet (solar battery back sheet) according to the present invention is shown in Fig. 2. In Fig. 2, a thin film (or a foil film) 11a is formed between the film 11 and the outdoor urethane adhesive 13. For example, Fig 2 shows an embodiment in which a metal thin film 11a is formed on the surface of the film 11 when the film 11 is a plastic film. The metal thin film 11a can be formed on the surface of the plastic film 11 by vapor deposition and like, and the solar battery back sheet of Fig. 2 can be obtained by laminating the metal thin film 11, on which surface the metal thin film 11a is formed, with the film 12 by interposing the adhesive for laminated sheets 13 therebetween.

[0060]

Examples of the metal to be deposited on the plastic film include aluminum, steel, copper and the like. It is possible to impart barrier properties to the plastic film by subjecting the film to vapor deposition. Silicon oxide or aluminum oxide is used as a vapor deposition material. The plastic film 11 as a base material may be either transparent, or white- or black-colored.

A plastic film made of polyvinyl chloride, polyester, a fluororesin, an acrylic resin and a polyolefin is used as the film 12. In order to impart heat resistance,

weatherability, rigidity, insulating properties and the like, a polyethylene terephthalate film or a polybutylene terephthalate film is preferably used. The films 11 and 12 may be either transparent or colored.

The film 12 and the deposited thin film 11a of the film 11 are laminated with each other using the adhesive 13 according to the present invention, and the films 11 and 12 are often laminated each other by a dry lamination method.

[0061]

Fig. 3 shows a sectional view of an example of a solar battery module as an embodiment of the outdoor material of the present invention. In Fig. 3, it is possible to obtain a solar battery module 1 by laying a glass plate 40, a sealing material 20 such as an ethylene-vinyl acetate resin (EVA) , plural solar battery cells 30 which are commonly connected with each other so as to generate a desired voltage, and a back sheet 10 over one another, and then fixing these members 10, 20, 30 and 40 using a spacer 50.

As mentioned above, since the back sheet 10 is a laminate of the plurality of the films 11 and 12, it is required for the urethane adhesive 13 to cause no peeling of the films 11 and 12 even when the back sheet 10 is exposed outdoors over a long term.

The solar battery cell 30 is often produced by using silicon, and is sometimes produced by using an organic resin containing a dye. In that case, the solar battery module 1 becomes an organic (dye sensitized) solar battery module. Since colorability is required of the organic (dye sensitized) solar battery, a transparent film is often used as the film 11 and the film 12 which compose the solar battery back sheet 10. Therefore, it is required for the adhesive for solar battery back sheets 13 to cause very little change in color difference and to have excellent weatherability, even when the adhesive is exposed outdoors over a long term.

[0062]

Main embodiments of the present invention will be shown below.

1. An adhesive for laminated sheets, comprising a urethane resin obtainable by mixing an acrylic polyol with an isocyanate compound; and a silane compound, wherein the acrylic polyol is obtainable by polymerizing a

2. The adhesive for laminated sheets according to the above 1, wherein the isocyanate compound comprises at least one selected from a trimethylolpropane adduct form, an

isocyanurate form, a biuret form, an allophanate form and a monomer of an isocyanate.

3. The adhesive for laminated sheets according to the above 1 or 2 , wherein the acrylic polyol has a glass transition temperature (Tg) of from -20°C to 20°C.

4. A laminated sheet obtainable by using the adhesive for laminated sheets according to any one of the above 1 to 3.

5. An outdoor material obtainable by using the laminated sheet according to the above 4.

6. A raw material comprising an acrylic polyol for

producing the adhesive for laminated sheets according to any one of the above 1 to 3 , wherein the acrylic polyol is obtainable by polymerizing a polymerizable monomer; the polymerizable monomer contains a monomer having a hydroxyl group and the other monomer; and the other monomer contains acrylonitrile .

Examples

[0063]

The present invention will be described below by way of Examples and Comparative Examples; these Examples are merely for illustrative purposes and are not meant to be limiting on the present invention.

[0064]

Synthetic Example (Al) (Acrylic Polyol)

In a four-necked flask equipped with a stirring blade, a thermometer and a reflux condenser, 100 g of ethyl

acetate (manufactured by Wako Pure Chemical Industries, Ltd.) was charged and refluxed at about 80°C. In the flask, 1 g of 2 , 2-azobisisobutyronitrile as a polymerization initiator was added and a mixture of monomers in each amount shown in Table 1 was continuously added dropwise over 1 hour and 30 minutes. After heating for 2 hours, a solution of an acrylic polyol (Al) having a non-volatile content (solids content) of 50.0% by weight was obtained.

The composition of the polymerizable monomer component used to synthesize the acrylic polyol (Al) , and physical properties of the obtained acrylic polyol (Al) are shown in Table 1.

[0065]

Synthetic Examples 2 to 7

In the same manner as in Synthetic Example 1, except that the composition of monomers used so as to synthesize the acrylic polyol (Al) was changed as shown in Table 1, acrylic polyols (A2) to (A' 6), and an acrylic polymer (A' 7) (having no hydroxyl group) were obtained. Physical

properties of the obtained acrylic polyols and acrylic polymer are shown in Table 1.

The polymerizable monomers and other components in Table 1 are shown below.

- Methyl methacrylate (MMA) : manufactured by Wako Pure Chemical Industries, Ltd.

- Butyl acrylate (BA) : manufactured by Wako Pure Chemical Industries, Ltd.

- Ethyl acrylate (EA) : manufactured by Wako Pure Chemical Industries, Ltd.

- Glycidyl methacrylate (GMA) : manufactured by Wako Pure Chemical Industries, Ltd.

- Acrylonitrile (AN) : manufactured by Wako Pure Chemical Industries, Ltd.

- 2 -Hydroxyethyl methacrylate (HEMA) : manufactured by Wako Pure Chemical Industries, Ltd.

- 2 -Hydroxyethyl acrylate (HEA) : manufactured by Wako Pure Chemical Industries, Ltd.

- Styrene (St) : manufactured by Wako Pure Chemical

Industries, Ltd.

- 2 , 2-Azobisisobutyronitrile (AIBN) : manufactured by Otsuka

Chemical Co., Ltd.

[0066]

Table 1

Unit of the value indicating the composition of the poiymerizable monomer is part by weight.

[0067]

<Calculation of Glass Transition Temperature (Tg) of

Acrylic Polyol and Acrylic Polymer>

Tgs of the acrylic polyols and acrylic polymer (Al) to (A ¹7 ) were calculated by the above-mentioned formula (i) using glass transition temperatures of homopolymers of the "polymerizable monomers" as the raw materials of the respective polyols and polymer.

Document values were, used as the Tgs of homopolymers of such as methyl methacrylate .

[0068]

Raw materials of the adhesives for laminated sheets used in Examples and Comparative Examples are shown below.

(A) Acrylic polyol

The acrylic polyols correspond to the acrylic polyols (Al) to (A5) shown in Table 1.

(A' ) Acrylic polyol'

The acrylic polyol' corresponds to the acrylic polyol (A' 6).

The acrylic polymer (having no hydroxyl group) corresponds to the acrylic polymer (A' 7) in Table 1.

[0069]

(B) Silane coupling agent

(Bl) 3 -Glycidoxypropyltrimethoxysilane ( BM-403 (trade name) manufactured by Shin-Etsu Chemical Co., Ltd.)

(B2) 3 -Glycidoxypropyltriethoxysilane (Z-6041 (trade name) manufactured by Dow Corning Toray Co., Ltd.)

(B3) 3 -Glycidoxypropylmethyldimethoxysilane (Z-6044 (trade name) manufactured by Dow Corning Toray Co., Ltd.)

(B4) 2- (3 , 4 -Epoxycyclohexyl) ethyltrimethoxysilane (KBM-303

(trade name) manufactured by Shin-Etsu Chemical Co., Ltd.)

(B5) Vinyltriacetoxysilane (Z-6075 (trade name)

manufactured by Dow Corning Toray Co., Ltd.)

(B6) 3 -Methacryloxypropyldimethoxysilane (SZ-6030 (trade name) manufactured by Dow Corning Toray Co., Ltd.)

(B7) 3 -Aminopropyltriethoxysilane (Z-6011 (trade name) manufactured by Dow Corning Toray Co., Ltd.)

(B'8) Isopropyl triisostearoyl titanate (PLENACT KR TTS

(trade name) manufactured by Ajinomoto Fine-Techno Co., Inc . )

[0070]

(C) Isocyanate compound

(CI) <Aliphatic> Isocyanurate of 1 , 6 -diisocyanatohexane (HDI) (Sumidur N3300 (trade name) manufactured by Sumitomo Bayer Urethane Co., Ltd., NCO% = 21.8%)

(C2) <Aliphatic> Biuret of 1 , 6 -diisocyanatohexane (HDI) (Sumidur N3200 (trade name) manufactured by Sumitomo Bayer Urethane Co., Ltd., NCO% = 23.0%)

(C3) <Aliphatic> Allophanate of 1 , 6 -diisocyanatohexane (HDI) (Takenato D178N (trade name) manufactured by MITSUI

TAKEDA CHEMICALS INC., NCO% = 19.2%)

(C4) <Alicylic> Isocyanurate trimer of isophorone

diisocyanate (IPDI) (VESTANATT 1890 (trade name) manufactured by EVONIK Industries, NCO% = 17.3%) (C5) <Aromatic> 4 , 4 ' -diphenylmethane diisocyanate (MDI) (MILLIONATE MT (trade name) manufactured by Nippon

Polyurethane Industry Co., Ltd., NCO% = 33.6%)

(C6) <Aromatic> TMP adduct of tolylene diisocyanate (TDI)

(Desmodur L75 (trade name) manufactured by Sumitomo Bayer

Urethane Co., Ltd., NCO% = 18.0%)

(C7) <Aromatic> Xylylene diisocyanate (XDI) monomer

(Takenato 500 ^' (trade name) manufactured by Mitsui Chemicals, Incorporated. ,. NCO% = 44.7%)

[0071]

A urethane resin is obtained by reacting the acrylic polyol with the isocyanate compound.

The below-mentioned adhesives for laminated sheets of Examples 1 to 17 and Comparative Examples 1 to 4 were produced by mixing the above-mentioned components.

Detailed compositions of the adhesives are shown in Tables 2 to 3. The production processes thereof were performed in accordance with the steps of Example 1. The obtained adhesives for laminated sheets were evaluated by the

following tests.

[0072]

Example 1

As shown in Table 2, 91.8 g of the acrylic polyol (Al) [183.6 g of an ethyl acetate solution of the acrylic polyol (Al) (solids content: 50.0% by weight)] was mixed with 2.8 g [3.0% based on 100% of the solids content of the acrylic polyol (Al)] of the silane coupling agent (Bl) , and then 5.4 g of the isocyanate compound (CI) was added, followed by mixing. Furthermore, ethyl acetate was added to the mixture to prepare an adhesive solution having a solids content of 30% by weight. Using this solution thus

prepared as an adhesive for laminated sheets, the following tests were carried out.

[0073]

First, the adhesive for laminated sheets of Example 1 was applied to a transparent polyethylene terephthalate (PET) sheet (O300EW36 (trade name) manufactured by

Mitsubishi Polyester Film Corporation) so that the weight of the solid component becomes 10 g/m² , and then dried at 80°C for 10 minutes to obtain an adhesive-coated PET sheet.

Then, a surface-treated transparent polyolefin film (linear low-density polyethylene film manufactured by

Futamura Chemical Co., Ltd. under the trade name of LL-XUMN #30) was laid on the adhesive-coated surface of the

adhesive-coated PET sheet so that the surface-treated surface was brought into contact with the adhesive-coated surface, and then both films were pressed using a planar press machine (manufactured by SHINTO Metal Industries Corporation under the trade name of ASF-5) under a pressing pressure of 1.0 MPa at 50 °C for 30 minutes. The thus pressed both films were aged at 50 °C for 7 days to obtain a film laminate 1 composed of a polyolefin film

(PE) /adhesive/PET sheet.

[0074]

A 30 μιη thick surface-treated white polyvinylidene fluoride film (Kynar film (trade name) manufactured by Arkema Inc.) was laid on the adhesive-coated surface of the adhesive-coated PET sheet so that the surface-treated surface was brought into contact with the adhesive-coated surface, and then both films were pressed using a planar press machine (ASF-5 (trade name) manufactured by SHINTO Metal Industries Corporation) under a pressing pressure (or closing pressure) of 1.0 MPa at 50°C for 30 minutes. The thus pressed both films were aged at 50 °C for 7 days to obtain a film laminate 2 composed of polyvinylidene

fluoride film (PVDF) /adhesive/PET sheet.

[0075]

Examples 2 to 17 and Comparative Examples 1 to 4

In the same manner as in Example 1, an adhesive-coated PET sheet, a film laminate 1 and a film laminate 2 were produced.

[0076]

<Evaluation> .

The adhesives for laminated sheets (adhesives for solar battery back sheets) of the Examples and the

adhesives of the Comparative Examples were evaluated by the following methods. The evaluation results are shown in Tables 2 to 3.

1. Evaluation of Initial Adhesion to Film

A film laminate 1 and a film laminate 2 were cut out into pieces of 15 mm in width. Using a tensile strength testing machine (TENSILON RTM-250 (trade name) manufactured by ORIENTEC Co., Ltd.), a 180° peel test was carried out under a room temperature environment at a testing speed of 100 mm/min. The evaluation criteria were as shown below.

A: Peel strength was 10 N/15 mm or more, or material fracture occurred.

B: Peel strength was 6 N/15 mm or more but less than 10 N/15 mm.

C: Peel strength was less than 6 N/15 mm.

The "material fracture" means that the base material "PVDF" or "PET" was fractured. Therefore, it means the strength of the adhesive per se was higher.

[0077]

2. Evaluation of Hydrolysis Resistance A film laminate 1 and a film laminate 2 were put in a thermo-hygrostat and maintained in a wet heat state in an atmosphere at 85 °C and humidity of 85%RH for 3,000 hours. Then, a peel test similar to the measurement of initial adhesion to a film was performed and the hydrolysis

resistance was evaluated.

A: Peel strength was 10 (N/15 mm) or more, or material fracture occurred.

B: Peel strength was 6 (N/15 mm) or more but less than 10 (N/15 mm) .

C: Peel strength was less than 6 (N/15 mm) .

[ 0078 ]

Table 2

Unit of value indicating the compositions of the components (A) to (C) is part by weight.

Part by weight of the component (A) is a value calculated on the solids content basis. [ 0079]

Table 3

Part by weight of the component (A) is a value calculated on the solids content basis.

The value of the NCO/OH equivalent ratio of Examples 15 to 17 is described as 1.0 + 1.0. This means that two types of isocyanate compounds were used, the NCO/OH equivalent ratio was 1.0 with respect to each isocyanate compound, and the total was 2.0. [0080]

As shown in Tables 2 to 3, the adhesives for laminated sheets of Examples 1 to 17 were excellent in initial adhesion to a film and hydrolysis resistance. The

adhesives for laminated sheets of Examples could suppress deterioration of adhesion even though the laminates of the polyethylene terephthalate (PET) film and the

polyvinylidene fluoride (PVDF) film were exposed to a severe environment. Therefore, the adhesives for laminated sheets of the Examples could each sufficiently fulfill a role as an adhesive for solar battery back sheets for which high-level durability is required.

[0081]

To the contrary, the adhesive of Comparative Example 1 contained no coupling agent, and therefore wettability of a surface of the base material (PVDF film, PET film)

deteriorated and adhesion between films was inferior as compared with the adhesives of the Examples.

The adhesive of Comparative Example 2 contained no silane coupling agent, but contained a titanate based coupling agent. Since the titanate based coupling agent had a strong catalytic activity against the urethanation reaction of the acrylic polyol (A) with the isocyanate compound (D) , the curing rate of the adhesive for laminated sheets became too high, thus causing deterioration of the initial adhesion to a film and of the hydrolysis resistance.

[0082]

In the adhesive of Comparative Example 3, the acrylic polyol (A' 6) - used as a raw material for the urethane resin - contained no acrylonitrile . Consequently, cohesive force of the adhesive per se decreased, and thus both initial adhesion to a film and hydrolysis resistance

deteriorated .

As the acrylic polyol (A' 7) - used as a raw material for the urethane resin - had no hydroxyl group, the

adhesive of Comparative Example 4 had no urethane bond, and thus initial adhesion to a film and hydrolysis resistance were drastically inferior.

Industrial Applicability

[0083]

The present invention provides an adhesive for

laminated sheets. The adhesive for laminated sheets

according to the present invention is suited as an adhesive for solar battery back sheets since it is excellent in initial adhesion to a film and is also excellent in long- term hydrolysis resistance at high temperature, resulting in remarkably enhanced durability against the environment.

Description of Reference Numerals [0084]

1: Solar battery module, 10: Laminated sheet (for example, Back sheet), 11: Film, 11a: Deposited thin film, 12: Film, 13: Adhesive layer, 20: Sealing material (EVA), 30: Solar battery cell, 40: Glass plate, 50: Spacer

Claims

1. An adhesive for laminated sheets, comprising:

a urethane resin obtainable by mixing an acrylic polyol with an isocyanate compound; and

a silane compound, wherein

the acrylic polyol is obtainable by polymerizing a polymerizable monomer;

the polymerizable monomer contains a monomer having a hydroxyl group and the other monomer; and

the other monomer contains acrylonitrile .

2. The adhesive for laminated sheets according to claim 1, wherein the isocyanate compound comprises at least one selected from a trimethylolpropane adduct form, an

3. The adhesive for laminated sheets according to claim 1 or 2, wherein the acrylic polyol has a glass transition temperature (Tg) of from -20 °C to 20 °C.

4. A laminated sheet obtainable by using the adhesive for laminated sheets according to any one of claims 1 to 3.

5. An outdoor material obtainable by using the laminated sheet according to claim 4.

6. A raw material comprising an acrylic polyol for producing the adhesive for laminated sheets according to any one of claims 1 to 3 , wherein

the acrylic polyol is obtainable by polymerizing a polymerizable monomer;

the other monomer contains acrylonitrile .