U.S. patent application number 15/198528 was filed with the patent office on 2016-10-27 for adhesive for laminated sheets.
The applicant listed for this patent is Henkel AG & Co. KGaA. Invention is credited to Shoko Ito, Noriyoshi Kamai, Yuichi Matsuki, Yasushi Yamada.
Application Number | 20160312092 15/198528 |
Document ID | / |
Family ID | 48444530 |
Filed Date | 2016-10-27 |
United States Patent
Application |
20160312092 |
Kind Code |
A1 |
Yamada; Yasushi ; et
al. |
October 27, 2016 |
Adhesive for Laminated Sheets
Abstract
An adhesive for laminated sheets comprising a urethane resin
obtainable by mixing an acrylic polyol with an isocyanate compound.
The acrylic polyol is obtained by polymerizing a mixture including
a first monomer having a hydroxyl group and acrylonitrile. The
isocyanate compound includes both an isocyanate compound having no
aromatic ring and an isocyanate compound having an aromatic ring.
Also cured reaction products of the adhesive and films laminated
using the adhesive.
Inventors: |
Yamada; Yasushi; (Osaka,
JP) ; Ito; Shoko; (Osaka, JP) ; Kamai;
Noriyoshi; (Hyogo, JP) ; Matsuki; Yuichi;
(Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Henkel AG & Co. KGaA |
Duesseldorf |
|
DE |
|
|
Family ID: |
48444530 |
Appl. No.: |
15/198528 |
Filed: |
June 30, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14518029 |
Oct 20, 2014 |
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15198528 |
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PCT/JP2013/062304 |
Apr 19, 2013 |
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14518029 |
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14286025 |
May 23, 2014 |
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PCT/JP2013/062304 |
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PCT/JP2012/080799 |
Nov 21, 2012 |
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14286025 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09J 175/12 20130101;
C08G 18/724 20130101; C09J 133/12 20130101; C09J 175/04 20130101;
H01L 31/049 20141201; B32B 27/08 20130101; B32B 2250/02 20130101;
B32B 2255/26 20130101; H01L 31/048 20130101; B32B 2457/12 20130101;
Y10T 428/31565 20150401; B32B 2307/712 20130101; B32B 2255/205
20130101; B32B 2367/00 20130101; B32B 27/32 20130101; B32B 27/36
20130101; B32B 2250/24 20130101; Y10T 428/31605 20150401; C08G
18/6229 20130101; C08F 220/1804 20200201; Y02E 10/50 20130101; B32B
7/12 20130101; C08F 220/18 20130101; B32B 2571/00 20130101; B32B
2323/00 20130101; C09J 133/08 20130101; B32B 2255/10 20130101; C08G
18/6262 20130101 |
International
Class: |
C09J 175/12 20060101
C09J175/12; B32B 15/04 20060101 B32B015/04; B32B 7/12 20060101
B32B007/12; C08F 220/18 20060101 C08F220/18; H01L 31/049 20060101
H01L031/049 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 25, 2011 |
JP |
2011-257268 |
Apr 23, 2012 |
JP |
2012-097638 |
Claims
1. An adhesive for laminated sheets, comprising a urethane resin
obtained by mixing an acrylic polyol with an isocyanate compound,
wherein the acrylic polyol is a polyol having a glass transition
temperature of from -20 to 20.degree. C., which polyol is obtained
by polymerizing a mixture comprising a first monomer having a
hydroxyl group and acrylonitrile; and the isocyanate compound
includes both an isocyanate compound having no aromatic ring
selected from an aliphatic isocyanate compound and an alicyclic
isocyanate compound and an isocyanate compound having an aromatic
ring wherein an equivalent ratio of an isocyanate group derived
from the isocyanate having an aromatic ring to a hydroxyl group
derived from the acrylic polyol is 0.5 or more.
2. The adhesive for laminated sheets according to claim 1, wherein
the polyol is obtained by polymerizing a mixture comprising a first
monomer having a hydroxyl group, a different second monomer and
acrylonitrile.
3. The adhesive for laminated sheets according to claim 1, wherein
the polyol is obtained by polymerizing a mixture comprising a first
monomer having a hydroxyl group, a different second monomer having
an ethylenic double bond and acrylonitrile.
4. (canceled)
5. The adhesive for laminated sheets according to claim 1, wherein
the acrylic polyol has a hydroxyl value of from 0.5 to 45
mgKOH/g.
6. The adhesive for laminated sheets according to claim 1, wherein
the second monomer includes a (meth)acrylic acid ester.
7. (canceled)
8. Cured reaction products of the adhesive of claim 1.
9. A laminated sheet comprising a first film bonded to a second
film by the adhesive of claim 1.
10. The laminated sheet of claim 9 wherein at least one of the
first film or second film is a metal film.
11. A solar battery backsheet comprising a first film bonded to a
second film by the adhesive of claim 1.
12. An outdoor material including a laminated sheet comprising the
adhesive for laminated sheets according to claim 1.
13. The adhesive for laminated sheets according to claim 1, wherein
an equivalent ratio of an isocyanate group derived from the
isocyanate having an aromatic ring to a hydroxyl group derived from
the acrylic polyol is 1.5:1 to 2.5:1.
14. The adhesive for laminated sheets according to claim 1, wherein
the acrylic polyol is obtained by polymerizing a mixture comprising
a first monomer having a hydroxyl group and 1 to 40 parts by weight
of acrylonitrile based on 100 parts by weight of the mixture.
15. The adhesive for laminated sheets according to claim 1, wherein
the isocyanate is selected from 1,6-diisocyanatohexane (HDI),
isophorone diisocyanate, tolylene diisocyanate (TDI) and
combinations thereof.
16. The adhesive for laminated sheets according to claim 1, wherein
the isocyanate is selected from 1,6-diisocyanatohexane (HDI) in
isocyanurate form, isophorone diisocyanate in isocyanurate form,
tolylene diisocyanate (TDI) as an adduct with trimethylolpropane
and combinations thereof.
17. The adhesive for laminated sheets according to claim 1, wherein
the isocyanate compound includes both an alicyclic isocyanate
compound and an isocyanate compound having an aromatic ring.
18. The adhesive for laminated sheets according to claim 1, wherein
the isocyanate compound includes an aliphatic isocyanate compound,
an alicyclic isocyanate compound and an isocyanate compound having
an aromatic ring.
Description
TECHNICAL FIELD
[0001] 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
[0002] 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 obtained by laminating a plurality of films to each other
using an adhesive. Examples of the film composing the laminate
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.
[0003] 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.
[0004] Since the laminate is exposed outdoors over a long term,
excellent durability is required of the 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 a conventional adhesive for laminated sheets.
[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.
[0006] 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 can become
peeled from the film 12, 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 high temperature over a long term.
[0007] Patent Documents 1 to 3 disclose, as examples of adhesives
for laminated sheets, urethane based adhesives for producing solar
battery protection sheets.
[0008] 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 Claim 1 and the
paragraph number 0048).
[0009] 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).
[0010] Patent Document 3 describes mixing an isocyanate curing
agent with an acrylic polyol to produce adhesives (see Table 1,
Table 2); a solar battery back sheet is produced by using these
adhesives (see paragraph 0107).
[0011] 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, it is hard to say that
the adhesive sufficiently meets the high requirements of consumers.
Furthermore, durability required of an adhesive for solar battery
back sheets is getting higher year by year, and it is required for
an adhesive for back sheets to have high adhesion. Since the solar
battery module is mainly used outdoors, high adhesion at high
temperature is required.
[0012] It is necessary that an adhesive for solar battery back
sheets has sufficient adhesion even at high temperature and can
maintain adhesion even when exposed outdoors over a long time, and
also has an acceptable curing rate and has higher adhesion
(particularly adhesion after aging) to a film base material. When a
solar battery back sheet is produced by using the adhesives of
Patent Documents 1 to 3, plural films composing the back sheet
(laminated sheet) may be peeled under severe outdoor environments
(at high temperature over a long period).
[0013] When heat between the back sheet 10 and the sealing agent 20
(see FIG. 3) excessively increases, the film 11 of the back sheet
10 and the sealing agent 20 are integrated with each other to form
a relatively thick laminate (the sealing agent 20, the film 11 and
the adhesive 13); the film 11 and the adhesive 13 (or the film 12)
may sometimes cause interfacial peeling due to the influence of
film thickening or heating history.
[0014] Patent Document 1: JP 2011-105819 A
[0015] Patent Document 2: JP 2010-238815 A
[0016] Patent Document 3: JP 2010-263193 A
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0017] 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 curing rate and initial
adhesion to a film after aging in the case of producing a laminate
(laminated sheet), and is also excellent in hydrolysis resistance
over a long term at high temperature; and, an outdoor material
obtainable by using the laminated sheet.
Means for Solving the Problems
[0018] The present inventors have intensively studied and found,
surprisingly, that it is possible to obtain an adhesive for
laminated sheets, which is excellent in curing rate and initial
adhesion to a film after aging in producing a laminated sheet, and
is also excellent in hydrolysis resistance over a long term at high
temperature, by using a specific polyol and a specific isocyanate
as raw materials of a urethane resin. Thus, the present invention
has been completed.
[0019] 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,
wherein the acrylic polyol is a polyol having a glass transition
temperature of from -20 to 20.degree. C., which polyol is
obtainable by polymerizing a polymerizable monomer; the
polymerizable monomer includes a monomer having a hydroxyl group
and the other monomer, and the other monomer includes
acrylonitrile; and the isocyanate compound includes both an
isocyanate compound having no aromatic ring and an isocyanate
compound having an aromatic ring.
[0020] The present invention provides, in an embodiment, the
adhesive for laminated sheets, wherein the isocyanate compound
having no aromatic ring is at least one selected from an aliphatic
isocyanate compound and an alicyclic isocyanate compound.
[0021] The present invention provides, in a preferred embodiment,
the adhesive for laminated sheets, wherein the other monomer
further includes a (meth)acrylic acid ester.
[0022] The present invention provides, in a more preferred
embodiment, the adhesive for laminated sheets, wherein the acrylic
polyol has a hydroxyl value of from 0.5 to 45 mgKOH/g.
[0023] The present invention provides, in the most preferred
embodiment, the adhesive for laminated sheets, wherein an
equivalent ratio of an isocyanate group derived from the isocyanate
having an aromatic ring to a hydroxyl group derived from the
acrylic polyol is 0.5 or more.
[0024] The present invention provides, in another aspect, a
laminated sheet obtainable by using the above adhesive for
laminated sheets.
[0025] The present invention provides, as a preferred aspect, an
outdoor material obtainable by using the laminated sheet.
Effects of the Invention
[0026] The adhesive for laminated sheets according to the present
invention comprises a urethane resin obtainable by mixing an
acrylic polyol with the isocyanate compounds defined below; the
acrylic polyol is a polyol having a glass transition temperature of
from -20 to 20.degree. C., which polyol is obtainable by
polymerizing a monomer having a hydroxyl group and at least one
other monomer, wherein the at least one other monomer includes
acrylonitrile; and said isocyanate compounds include both an
isocyanate compound having no aromatic ring and an isocyanate
compound having an aromatic ring. Therefore, the adhesive for
laminated sheets is excellent in curing rate and initial adhesion
to a film after aging in producing a laminated sheet, is also
excellent in hydrolysis resistance over a long period at high
temperature and is excellent in overall balance. The adhesive of
the present invention is preferably used in outdoor materials, and
is particularly useful as an adhesive for solar battery protection
sheets.
[0027] The adhesive for laminated sheets according to the present
invention is preferably used as an adhesive for solar battery
protection sheets exposed to severe environment, particularly as an
adhesive for solar battery back sheets, since initial adhesion
after aging and long-term hydrolysis resistance at high temperature
may be further improved when the isocyanate compound having no
aromatic ring contains at least one selected from an aliphatic
isocyanate compound and an alicyclic isocyanate compound.
[0028] The adhesive according to the present invention can show
improved initial adhesion to a film after aging when the other
monomer further includes a (meth)acrylic acid ester.
[0029] In the adhesive for laminated sheets according to the
present invention, when the acrylic polyol has a hydroxyl value of
from 0.5 to 45 mgKOH/g, initial adhesion to a film after aging is
more improved and also hydrolysis resistance is improved. In
particular, when a solar battery back sheet is produced by
laminating a plurality of films using the adhesive of the present
invention, the films and the adhesive become much less likely to
cause interfacial peeling.
[0030] In the adhesive for laminated sheets according to the
present invention, when an equivalence ratio of isocyanate groups
derived from the isocyanate having an aromatic ring to hydroxyl
groups derived from the acrylic polyol is 0.5 or more, heat
resistance is more improved and long-term hydrolysis resistance at
high temperature is more improved.
[0031] The laminated sheet according to the present invention is
obtainable by using the above adhesive, and is therefore excellent
in productivity and also can prevent peeling of the film from the
adhesive when exposed outdoors over a long term from the beginning
of lamination.
[0032] The outdoor material according to the present invention is
obtainable by using the above laminated sheet, and is therefore
excellent in productivity, and is less likely to suffer poor
appearance and is also excellent in durability.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a sectional view of an embodiment of the laminated
sheet of the present invention.
[0034] FIG. 2 is a sectional view of another embodiment of the
laminated sheet of the present invention.
[0035] 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
[0036] The adhesive for solar battery back sheets according to the
present invention includes a urethane resin obtainable by mixing an
acrylic polyol with an isocyanate compound.
[0037] The urethane resin according to the present invention is a
polymer obtainable by mixing and reacting the acrylic polyol with
the isocyanate compound, and has a urethane bond. hydroxyl group of
the acrylic polyol reacts with an isocyanate group.
[0038] The acrylic polyol is obtainable by the addition
polymerization of a polymerizable monomer, and the polymerizable
monomer includes a "monomer having a hydroxyl group" and the "other
monomer". 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.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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 for laminated sheets 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.
[0043] 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 if 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".
[0044] In the present invention, it is preferred to include at
least one monomer 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 monomer selected from methyl (meth)acrylate, ethyl
(meth)acrylate, and butyl (meth)acrylate.
[0045] 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.
[0046] The "acrylonitrile" is a compound represented by the general
formula: CH.sub.2.dbd.CH--CN, and is also called acrylic nitrile,
acrylic acid nitrile, or vinyl cyanide.
[0047] The acrylonitrile is preferably contained in the amount of
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 amount of the acrylonitrile is within the above range, it is
possible to obtain an adhesive for solar battery back sheets, which
shows an excellent balance of coat-ability, initial adhesion to a
film after aging, and adhesion at high temperature.
[0048] 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".
[0049] 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
monomer. For example, the above-mentioned polymerizable monomer 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 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.
[0050] 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.
[0051] The "polymerization initiator" is preferably a compound
which can accelerate the polymerization of the polymerizable
monomer when added 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).
[0052] A chain transfer agent can be appropriately used for the
polymerization in the present invention so as 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.
[0053] As mentioned above, the acrylic polyol is obtainable by
polymerizing the polymerizable monomer. From the viewpoint of
coat-ability of the adhesive, the weight average molecular weight
(Mw) 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.degree. C., and then the Mw is determined by
conversion of an observed molecular weight based on a calibration
curve which is obtained by using polystyrene having a monodisperse
molecular weight as a standard reference material.
[0054] A glass transition temperature (Tg) of the acrylic polyol
can be set by adjusting a mass fraction of a monomer to be 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:
1/Tg=W1/Tg1+W2/Tg2+ . . . +Wn/Tgn (i):
where Tg in the above formula (i) denotes the glass transition
temperature of the acrylic polyol, each of W1, W2, . . . , Wn
denotes a mass fraction of each monomer, and each of Tg1, Tg2, . .
. , and Tgn denotes a glass transition temperature of a homopolymer
of each corresponding monomer.
[0055] 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.
[0056] In the present specification, the glass transition
temperatures of homopolymers of the following monomers are as
follows.
Methyl methacrylate: 105.degree. C. n-Butyl acrylate: -54.degree.
C. Ethyl acrylate: -20.degree. C. 2-Hydroxyethyl methacrylate:
55.degree. C. 2-Hydroxyethyl acrylate: -15.degree. C. Glycidyl
methacrylate: 41.degree. C.
Acrylonitrile: 130.degree. C.
Styrene: 105.degree. C.
[0057] In the present invention, the glass transition temperature
of the acrylic polyol is preferably from -20.degree. C. to
20.degree. C., more preferably -15.degree. C. to 20.degree. C., and
particularly preferably -10.degree. C. to 15.degree. C., from the
viewpoint of the initial adhesion to a film after aging. When the
glass transition temperature is lower than -20.degree. C., the
adhesive may cause decrease in cohesive force, resulting in
deterioration of hydrolysis resistance. When the glass transition
temperature is higher than 20.degree. C., the initial adhesion to a
film after aging may decrease since the adhesive may become too
hard.
[0058] 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 5 to 35 mgKOH/g. When the hydroxyl
value of the acrylic polyol is within the above range, it is
possible to obtain the adhesive which after aging, is excellent in
initial adhesion, adhesion at high temperature, and hydrolysis
resistance. Particularly, 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.
[0059] 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).
Hydroxyl value=[(weight of (meth)acrylate having a hydroxyl
group)/(molecular weight of (meth)acrylate having a hydroxyl
group)].times.(mole number of hydroxyl groups contained in 1 mol of
(meth)acrylate monomer having a hydroxyl group).times.(formula
weight of KOH.times.1,000)/(weight of the acrylic polyol) (ii):
[0060] In the present invention, the isocyanate compound includes
not only a monomer, but also all of a biuret form, an isocyanate
form, a polyhydric alcohol adduct and an allophanate form, and
mainly, it is roughly 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 alcohol, but the polyhydric alcohol is not limited only
to the TMP.
[0061] Examples of the isocyanate having no aromatic ring include
an "aliphatic isocyanate" and an "alicyclic isocyanate".
[0062] 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.
[0063] 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.
[0064] 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.
[0065] 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.
[0066] 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 the 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.
[0067] 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.
[0068] Since xylylene diisocyanate
(OCN--CH.sub.2--C.sub.6H.sub.4--CH.sub.2--NCO) has an aromatic
ring, it corresponds to the aromatic isocyanate even though the
isocyanate groups are not directly combined with the aromatic
ring.
[0069] In the present invention, the isocyanate compound is not
particularly limited as long as the objective urethane adhesive of
the present invention can be obtained, and 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 the
initial adhesion to a film after aging, the curing time, and the
hydrolysis resistance.
[0070] 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 with
trimethylolpropane.
[0071] 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.
[0072] 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, particularly 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 exhibits more improved curing rate, is excellent in heat
resistance and shows improved hydrolysis resistance at high
temperature.
[0073] The adhesive for laminated sheets 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.
[0074] 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 for laminated sheets according to the present
invention can be obtained.
[0075] 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.
[0076] 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.
[0077] 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, a
benzotriazole based compound and the like.
[0078] The adhesive for laminated sheets according to the present
invention can further contain other components as long as the
objective adhesive can be obtained.
[0079] 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.
[0080] Examples of the "other component" include a catalyst, a
tackifier resin, a pigment, a plasticizer, a flame retardant, a wax
and the like.
[0081] Examples of the "catalyst" include a metal catalyst, a
non-metal catalyst and the like.
[0082] Examples of the "metal catalyst" include a tin catalyst
(trimethyltin laurate, trimethyltin hydroxide, stannous octoate,
dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate,
etc.) and a lead based catalyst (lead oleate, lead naphthenate,
lead octoate, etc.), and examples of the other metal catalyst
include naphthenic acid metal salt such as cobalt naphthenate,
bismuth octoate, sodium persulfate, potassium persulfate and the
like.
[0083] The "non-metal catalyst" is preferably an amine based
catalyst, and more preferably a tertiary amine based catalyst.
Examples of the amine based catalyst include 1,2-dimethylimidazole,
triethylenediamine, tetraethylenediamine,
tetramethylhexylenediamine, diazabicycloalkenes,
dialkylaminoalkylamines and the like.
[0084] 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.
[0085] Examples of the "pigment" include titanium oxide, carbon
black and the like.
[0086] Examples of the "plasticizer" include dioctyl phthalate,
dibutyl phthalate, diisononyl adipate, dioctyl adipate, mineral
spirit and the like.
[0087] 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.
[0088] The "wax" is preferably a wax such as a paraffin wax and a
microcrystalline wax.
[0089] 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 mPas or more, coatability of
the adhesive may deteriorate. If a solvent is further 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.
[0090] The adhesive for laminated sheets of the present invention
can be produced by mixing the above-mentioned urethane resin, and
an ultraviolet absorber, an antioxidant, a light stabilizer and/or
other components which may be optionally added. There is no
particular limitation on the mixing method as long as the objective
adhesive for laminated sheets 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 curing rate and initial adhesion to
a film after aging, and is also excellent in overall balance.
[0091] Therefore, a laminated sheet is produced by laminating a
plurality of adherends using the adhesive of the present invention,
and the obtained laminated sheet is used for the production of
various outdoor materials.
[0092] 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).
[0093] It is required for an adhesive for producing solar battery
modules, among the adhesive for laminated sheets, to have a
particularly high level of 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.
[0094] 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
adhesive of the present invention are laminated with each other to
complete the solar battery back sheet.
[0095] 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.
[0096] 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.
[0097] 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 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 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.
[0098] 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.
[0099] A plastic film made of polyvinyl chloride, polyester, a
fluororesin or an acrylic resin 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.
[0100] The deposited thin film 11a of the film 11 and the film 12
are laminated 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.
[0101] 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.
[0102] 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 though the back sheet 10 is exposed outdoors over a long
term.
[0103] 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 even though the
adhesive is exposed outdoors over a long term, and to have
excellent weatherability.
[0104] In the present invention, even when the sealing material 20
and the back sheet 10 are integrated with each other, the adhesive
13 is not peeled from the film 11.
[0105] 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,
wherein
[0106] the acrylic polyol is a polyol having a glass transition
temperature of from -20 to 20.degree. C., which polyol is
obtainable by polymerizing a polymerizable monomer;
[0107] the polymerizable monomer includes a monomer having a
hydroxyl group and the other monomer, and the other monomer
includes acrylonitrile; and
[0108] the isocyanate compound includes both an isocyanate compound
having no aromatic ring and an isocyanate compound having an
aromatic ring.
2. The adhesive for laminated sheets according to the above 1,
wherein the isocyanate compound having no aromatic ring is at least
one selected from an aliphatic isocyanate compound and an alicyclic
isocyanate compound. 3. The adhesive for laminated sheets according
to the above 1 or 2, wherein the other monomer further includes a
(meth)acrylic acid ester. 4. The adhesive for laminated sheets
according to any one of the above 1 to 3, wherein the acrylic
polyol has a hydroxyl value of from 0.5 to 45 mgKOH/g. 5. The
adhesive for laminated sheets according to any one of the above 1
to 4, wherein an equivalent ratio of an isocyanate group derived
from the isocyanate having an aromatic ring to a hydroxyl group
derived from the acrylic polyol is 0.5 or more. 6. A laminated
sheet obtainable by using the adhesive for laminated sheets
according to any one of the above 1 to 5. 7. An outdoor material
obtainable by using the laminated sheet according to the above
6.
EXAMPLES
[0109] The present invention will be described below by way of
Examples and Comparative Examples, and these Examples are merely
for illustrative purposes and are not meant to be limiting on the
present invention.
Synthesis of Acrylic Polyol
Synthetic Example (A1)
Acrylic Polyol
[0110] 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.degree. 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 having a
non-volatile content (solid content) of 50.0% by weight was
obtained.
[0111] Composition of polymerizable monomer components of the
acrylic polyol (polymer 1), and physical properties of the obtained
acrylic polymer 1 are shown in Table 1.
Synthetic Examples 2 to 10
[0112] In the same manner as in Synthetic Example 1, except that
the composition of the monomers used in the synthesis of the
acrylic polyol (A1) was changed as shown in Tables 1 to 2, an
acrylic polyol (A2) to an acrylic polyol (A'9) and an acrylic
polymer (A'10) were obtained. Physical properties of the obtained
polymers are shown in Tables 1 to 2.
[0113] The polymerizable monomers and other components in Table 1
are shown below.
[0114] Methyl methacrylate (MMA): manufactured by Wako Pure
Chemical Industries, Ltd.
[0115] Butyl acrylate (BA): manufactured by Wako Pure Chemical
Industries, Ltd.
[0116] Ethyl acrylate (EA): manufactured by Wako Pure Chemical
Industries, Ltd.
[0117] Glycidyl methacrylate (GMA): manufactured by Wako Pure
Chemical Industries, Ltd.
[0118] Acrylonitrile (AN): manufactured by Wako Pure Chemical
Industries, Ltd.
[0119] 2-Hydroxyethyl methacrylate (HEMA): manufactured by Wako
Pure Chemical Industries, Ltd.
[0120] 2-Hydroxyethyl acrylate (HEA): manufactured by Wako Pure
Chemical Industries, Ltd.
[0121] Styrene (St): manufactured by Wako Pure Chemical Industries,
Ltd.
[0122] 2,2-Azobisisobutyronitrile (AIBN): manufactured by Otsuka
Chemical Co., Ltd.
[0123] n-Dodecylmercaptan (nDM): manufactured by NOF
CORPORATION
TABLE-US-00001 TABLE 1 Synthetic Examples of acrylic polyol 1 2 3 4
5 6 St 2 3 2 0 0 0 MMA 19 22 44 39 39 39 BA 67 56 42 45 41 50 EA 0
0 0 0 0 0 GMA 0 2 0 0 0 0 AN 10 15 10 10 10 10 HEMA 2 2 0 6 10 1
HEA 0 0 2 0 0 0 AIBN 1 1 1 1 1 1 Tg (.degree. C.) of -18 -4 16 11
16 5 acrylic polyol Hydroxyl value 8.6 8.6 9.7 25.9 43.1 4.3
(mgKOH/g) Weight average 40,000 41,000 36,000 35,000 40,000 42,000
molecular weight Polymer A1 A2 A3 A4 A5 A6
TABLE-US-00002 TABLE 2 Synthetic Examples of acrylic polyol 7 8 9
10 St 2 0 0 3 MMA 3 35 44 22 BA 73 0 54 58 EA 0 57 0 0 GMA 0 0 0 2
AN 20 6 0 15 HEMA 2 2 2 0 HEA 0 0 0 0 AIBN 1 1 1 1 Tg (.degree. C.)
of -24 22 -9 -6 acrylic polyol Hydroxyl value 8.6 8.6 8.6 0
(mgKOH/g) Weight average 45,000 42,000 43,000 40,000 molecular
weight Polymer A'7 A'8 A'9 A'10
Calculation of Glass Transition Temperature (Tg) of Acrylic
Polymer
[0124] Tgs of (A1) to (A'10) were calculated by the above-mentioned
equation (i) using a glass transition temperature of a homopolymer
of a "polymerizable monomer" as a raw material of each polymer.
[0125] The document value was used as Tg of each homopolymer such
as methyl methacrylate.
Production of Adhesive for Laminated Sheets
[0126] Raw materials of adhesives for laminated sheets used in
Examples and Comparative Examples are shown below.
(A) Acrylic Polyol
[0127] The acrylic polyols correspond to (A1) to (A6) shown in
Table 1.
(A') Acrylic Polyol'
[0128] The acrylic polyol' corresponds to (A'7) to (A'9) shown in
Table 2.
[0129] The acrylic polymer (having no hydroxyl group) corresponds
to the acrylic polymer (A'10) in Table 2.
(B) Isocyanate Compound
(B1) Aliphatic Isocyanate
[0130] (Isocyanurate form of 1,6-diisocyanatohexane (HDI): Sumidur
N3300 (trade name) manufactured by Sumitomo Bayer Urethane Co.,
Ltd.)
(B2) Alicyclic Isocyanate
[0131] (Isocyanurate form of isophorone diisocyanate (IPDI):
VESTANAT T1890/100 (trade name) manufactured by EVONIK
Industries)
(B3) Aromatic Isocyanate
[0132] (4,4'-Diphenylmethane diisocyanate (MDI): MILLIONATE MT
(trade name) manufactured by Nippon Polyurethane Industry Co.,
Ltd.)
(B4) Aromatic Isocyanate
[0133] (Adduct form of trimethylolpropane to tolylene diisocyanate
(TDI): Desmodur L75 (trade name) manufactured by Sumitomo Bayer
Urethane Co., Ltd.)
(B5) Aromatic Isocyanate
[0134] (Xylylene diisocyanate (XDI): Takenato 500 (trade name)
manufactured by Mitsui Chemicals, Incorporated.)
(C) Curing Catalyst
(C1) Tin Catalyst
[0135] Stannous octoate (U-28 (trade name) manufactured by NITTO
KASEI KOGYO K.K.)
(C2) Bismuth Catalyst
[0136] Bismuth octoate (PUCAT 25 (trade name) manufactured by NIHON
KAGAKU SANGYO CO., LTD.)
(C3) Tertiary Amine Catalyst
[0137] 1,2-Dimethylimidazole (TOYOCAT DMI (trade name) manufactured
by TOSOH CORPORATION)
[0138] A urethane resin is obtained by reacting the acrylic polyol
with the isocyanate compound.
[0139] The below-mentioned adhesives for laminated sheets of
Examples 1 to 16 and Comparative Examples 1 to 6 were produced by
mixing the above-mentioned components. Detailed compositions of the
adhesives are shown in Tables 3 to 6, and the production process is
performed in accordance with the process of Example 1. The obtained
adhesives for laminated sheets were evaluated by the following
tests.
Example 1
Production of Adhesive for Laminated Sheets
[0140] As shown in Table 3, 95.3 g of the acrylic polyol (A1)
[190.6 g of an ethyl acetate solution of the acrylic polyol (A1)
(solid content: 50.0% by weight)] and 0.048 g of (C1) were weighed
and mixed, and then 2.8 g of (B1) and 1.9 g of (B3) were added to
the mixture. 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.
Production of Adhesive-Coated PET Sheet 1 and Film Laminate 2
[0141] 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/m.sup.2, and then dried at 80.degree. C. for 10 minutes to obtain
an adhesive-coated PET sheet 1.
[0142] Then, a 50 .mu.m thick surface-treated transparent
polyolefin film (50 .mu.m thick linear low-density polyethylene
film LL-XUMN #30 (trade name) manufactured FUTAMURA CHEMICAL CO.,
LTD.) was laid on the adhesive-coated surface of the
adhesive-coated PET sheet 1 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.degree. C.
for 30 minutes. Both films were aged at 50.degree. C. for 3 days to
obtain a 1 mm thick film laminate 2 composed of polyolefin
film/adhesive/PET sheet.
Production of Film Laminate 3
[0143] Twenty polyolefin (polyethylene) films (LL-XUMN #30) were
laid on a polyolefin (polyethylene) film of the film laminate 2
and, after laying a 1 mm thick spacer on a planar press machine
(ASF-5 (trade name) manufactured by SHINTO Metal Industries
Corporation), twenty polyolefin (polyethylene) films were
integrated with each other by hot pressing under a pressing
pressure (or closing pressure) of 1.0 MPa at 150.degree. C. for 3
minutes to obtain a 1 mm thick film laminate 3 composed of
polyolefin film/adhesive/PET sheet.
Evaluation
[0144] The adhesives for solar battery back sheets were evaluated
by the following methods. The evaluation results are shown in
Tables 3 to 6.
1. Evaluation of Initial Adhesion to Film after Aging
[0145] The film laminate 2 was 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 peel test was
carried out under a room temperature environment at a tensile speed
of 100 mm/min and 180.degree.. The evaluation criteria were as
shown below.
[0146] A: Peel strength was 10 N/15 mm or more.
[0147] B: Peel strength was 6 N/15 mm or more but less than 10 N/15
mm.
[0148] C: Peel strength was 1 N/15 mm or more but less than 6 N/15
mm.
2. Evaluation of Curing Rate (Appearance after Pressure Cooker
(PCT) Test)
[0149] With respect to a film laminate 2 aged at 50.degree. C. for
3 days, a curing rate was evaluated by an acceleration test using
pressurized steam.
[0150] The film laminate 2 was cut out into an A5 size and
evaluation was performed using a high pressure cooker (manufactured
by Yamato Scientific Co., Ltd. under the trade name of autoclave
SP300 (trade name)). After continuously keeping a wet heat state at
121.degree. C. under 1.4 MPa for 100 hours, presence or absence of
floating and peeling were visually observed. The evaluation
criteria were as follows.
[0151] A: Neither lifting nor peeling of film was observed.
[0152] D: Both lifting and peeling of film were observed
3. Evaluation of Hydrolysis Resistance
[0153] A film laminate 2 was put in a thermo-hygrostat and
maintained in a wet heat state in an atmosphere at 85.degree. C.
and 85% RH for 3,000 hours. Then, a peel test similar to the
measurement of initial adhesion to a film after aging was
performed, and hydrolysis resistance was evaluated.
[0154] A: Peel strength was 10 (N/15 mm) or more, or material
fracture occurred.
[0155] B: Peel strength was 6 (N/15 mm) or more but less than 10
(N/15 mm).
[0156] C: Peel strength was 1 (N/15 mm) or more but less than 6
(N/15 mm).
4. Adhesion (1 mm Thick Polyolefin Film)
[0157] With respect to a film laminate 3, a peel test similar to
the measurement of initial adhesion to a film after aging was
performed, and adhesion was evaluated.
[0158] A: Peel strength was 10 (N/15 mm) or more.
[0159] B: Peel strength was 6 (N/15 mm) or more but less than 10
(N/15 mm).
[0160] C: Peel strength was 1 (N/15 mm) or more but less than 6
(N/15 mm).
5. Hydrolysis Resistance (1 mm Thick Polyolefin Film)
[0161] A film laminate 3 was put in a thermo-hygrostat and
maintained in a wet heat state in an atmosphere at 85.degree. C.
and 85% RH for 1,000 hours. Then, a peel test similar to the
measurement of initial adhesion to a film after aging was
performed, and hydrolysis resistance was evaluated.
[0162] A: Peel strength was 10 (N/15 mm) or more, or material
fracture occurred.
[0163] B: Peel strength was 5 (N/15 mm) or more but less than 10
(N/15 mm).
[0164] C: Peel strength was 0 (N/15 mm) or more but less than 5
(N/15 mm).
[0165] D: Delamination (a laminated sheet was not formed).
TABLE-US-00003 TABLE 3 Examples 1 2 3 4 5 6 Acrylic polyol (A) A1
95.3 (having solid A2 95.3 95.3 content of A3 94.8 50%)*1 A4 87.1
A5 80.4 A6 A'7 A'8 A'9 A'10 Isocyanate B1 2.8 2.8 2.8 3.2 7.8 11.9
compound (B) B2 B3 1.9 1.9 1.9 2.0 5.1 7.7 B4 B5 Equivalent ratio
(1.0 + 0 + 1.0)/1 (1.0 + 0 + 1.0)/1 (1.0 + 0 + 1.0)/1 (1.0 + 0 +
1.0)/1 (1.0 + 0 + 1.0)/1 (1.0 + 0 + 1.0)/1 NCO/OH*2 Curing catalyst
C1 0.048 0.048 0.047 0.044 0.040 (C) C2 C3 Initial adhesion after A
A A A B B aging Appearance after PCT A A A A A A test Hydrolysis
resistance B A A A B B Adhesion B A A A A A (1 mm thick PE)
Hydrolysis resistance B B B A B A (1 mm thick PE) *1Mass based on
100% solids content was shown. *2Numerical value of NCO indicates
each equivalent ratio of B1 (aliphatic isocyanate), B2 (alicyclic
isocyanate) and B3 to B5 (polyisocyanate having an aromatic ring)
from the left side.
TABLE-US-00004 TABLE 4 Examples 7 8 9 10 11 Acrylic polyol (A) A1
(having solid A2 94.7 95.0 96.2 95.5 content of A3 50%)*1 A4 A5 A6
97.6 A'7 A'8 A'9 A'10 Isocyanate B1 1.5 1.4 2.9 0.9 compound (B) B2
3.5 1.8 B3 0.9 1.8 1.8 0.9 3.6 B4 B5 Equivalent ratio (1.0 + 0 +
1.0)/1 (0 + 1.0 + 1.0)/1 (0.5 + 0.5 + 1.0)/1 (1.0 + 0 + 0.5)/1 (0.3
+ 0 + 2.0)/1 NCO/OH*2 Curing catalyst C1 0.049 0.047 0.143 0.048
0.024 (C) C2 C3 Initial adhesion after A A A B A aging Appearance
after PCT A A A A A test Hydrolysis resistance A A A B A Adhesion A
A A B A (1 mm thick PE) Hydrolysis resistance B B B B A (1 mm thick
PE) *1Mass based on 100% solids content was shown. *2Numerical
value of NCO indicates each equivalent ratio of B1 (aliphatic
isocyanate), B2 (alicyclic isocyanate) and B3 to B5 (polyisocyanate
having an aromatic ring) from the left side.
TABLE-US-00005 TABLE 5 Examples 12 13 14 15 16 Acrylic polyol (A)
A1 (having solid A2 93.8 95.8 93.7 95.3 95.3 content of A3 50%)*1
A4 A5 A6 A'7 A'8 A'9 A'10 Isocyanate B1 2.8 2.9 2.8 2.8 2.8
compound (B) B2 B3 1.8 1.9 1.9 B4 3.4 1.7 B5 1.3 Equivalent ratio
(1.0 + 0 + 1.0)/1 (1.0 + 0 + 1.0)/1 (1.0 + 1.0 + 0.5)/1 (1.0 + 0 +
1.0)/1 (1.0 + 0 + 1.0)/1 NCO/OH*2 Curing catalyst C1 0.047 0.048
0.047 (C) C2 0.191 C3 0.381 Initial adhesion after A A A A A aging
Appearance after PCT A A A A A test Hydrolysis resistance A A A A A
Adhesion A A A A A (1 mm thick PE) Hydrolysis resistance B B B B B
(1 mm thick PE) *1Mass based on 100% solids content was shown.
*2Numerical value of NCO indicates each equivalent ratio of B1
(aliphatic isocyanate), B2 (alicyclic isocyanate) and B3 to B5
(polyisocyanate having an aromatic ring) from the left side.
TABLE-US-00006 TABLE 6 Comparative Examples 1 2 3 4 5 6 Acrylic
polyol (A) A1 (having solid A2 95.7 97.2 content of A3 50%)*1 A4 A5
A6 A'7 95.3 A'8 95.3 A'9 95.3 A'10 95.3 Isocyanate B1 2.8 2.8 2.8
2.8 4.3 compound (B) B2 B3 1.9 1.9 1.9 1.9 2.8 B4 B5 Equivalent
ratio (1.0 + 0 + 1.0)/1 (1.0 + 0 + 1.0)/1 (1.0 + 0 + 1.0)/1 -- (1.5
+ 0 + 0)/1 (0 + 0 + 1.5)/1 NCO/OH*2 Curing catalyst C1 0.048 0.048
0.048 0.048 0.144 0.049 (C) C2 C3 Initial adhesion after B C B C B
C aging Appearance after PCT A D D D D A test Hydrolysis resistance
B C C C C C Adhesion C A C C B A (1 mm thick PE) Hydrolysis
resistance D B D D C D (1 mm thick PE) *1Mass based on 100% solids
content was shown. *2Numerical value of NCO indicates each
equivalent ratio of B1 (aliphatic isocyanate), B2 (alicyclic
isocyanate) and B3 to B5 (polyisocyanate having an aromatic ring)
from the left side.
[0166] As shown in Tables 3 to 5, the adhesives for laminated
sheets of Examples 1 to 16 were excellent in adhesion to a film
after aging, curing rate (appearance after pressure cooker test),
hydrolysis resistance (at high temperature and for a long time),
and adhesion (1 mm thick film sheet) and hydrolysis resistance (1
mm thick polyolefin film). Therefore, the adhesives for laminated
sheets, having these various performances, could sufficiently
fulfill a role as adhesives for solar battery back sheets which are
to be exposed to a severe environment.
[0167] To the contrary, the adhesives of Comparative Examples were
inferior in at least one evaluated performance when compared with
the adhesives for laminated sheets of the Examples, as shown in
Table 6.
[0168] In the adhesive of Comparative Example 1, adhesion (1 mm
thick film sheet) and hydrolysis resistance (1 mm thick film sheet)
deteriorated, since the acrylic polyol (A'7) had too low glass
transition temperature.
[0169] In the adhesive of Comparative Example 2, adhesion to a film
after aging deteriorated and appearance after a pressure cooker
test became poor, since the acrylic polyol (A'8) had too high a
glass transition temperature.
[0170] In the adhesive of Comparative Example 3, since the
polymerizable monomer did not contain acrylonitrile in synthesizing
the acrylic polyol (A'9), a cohesive force of the adhesive
decreased and thus adhesion and hydrolysis resistance (1 mm thick
film) deteriorated.
[0171] In the adhesive of Comparative Example 4, since the acrylic
resin having no hydroxyl group (A'10) in place of the acrylic
polyol was simply mixed with the isocyanate compound, the adhesive
did not have a urethane bond and did not undergo curing. As is
apparent from Table 6, the adhesive of Comparative Example 4 was
drastically inferior in adhesion and hydrolysis resistance when
compared with other Comparative Examples.
[0172] In the adhesive of Comparative Example 5, since an aromatic
isocyanate was not used and only an aliphatic isocyanate was added,
appearance after a pressure cooker test was inferior due to low
curing rate, and also hydrolysis resistance was also inferior.
[0173] In the adhesive of Comparative Example 6, since neither an
aliphatic isocyanate nor an alicyclic isocyanate was used and only
an aliphatic isocyanate was used, initial adhesion to a film after
aging, and hydrolysis resistance were inferior.
INDUSTRIAL APPLICABILITY
[0174] 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 curing rate and initial adhesion to a film
after aging, and is also excellent in long-term hydrolysis
resistance at high temperature, resulting in remarkably enhanced
durability against a severe environment.
DESCRIPTION OF REFERENCE NUMERALS
[0175] 1: Solar battery module, 10: 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
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