U.S. patent application number 14/377026 was filed with the patent office on 2015-01-01 for separator.
This patent application is currently assigned to NITTO DENKO CORPORATION. The applicant listed for this patent is NITTO DENKO CORPORATION. Invention is credited to Asuka Endo, Rie Hayashiuchi, Shigeki Ishiguro, Yuka Sekiguchi, Hiroki Senda, Satomi Yoshie.
Application Number | 20150004404 14/377026 |
Document ID | / |
Family ID | 48947192 |
Filed Date | 2015-01-01 |
United States Patent
Application |
20150004404 |
Kind Code |
A1 |
Senda; Hiroki ; et
al. |
January 1, 2015 |
SEPARATOR
Abstract
The present invention provides a separator including a separator
substrate composed of a polylactic acid film or sheet having tear
strength so as not to break or tear during production or processing
of the separator. The separator is a separator including a
separator substrate and a removable pressure-sensitive adhesive
layer on at least one surface of the separator substrate, wherein
the separator substrate is composed of a polylactic acid film or
sheet comprising polylactic acid (A) wherein the tear strength of
the film or sheet is not less than 100 N/mm when the film or sheet
is torn at least in a flow direction (MD), a rate of dimensional
change due to heating is not more than .+-.3% in the flow direction
(MD) and a transverse direction (TD), and a rate of dimensional
change due to loaded heating is not more than .+-.3% in the flow
direction (MD).
Inventors: |
Senda; Hiroki; (Osaka,
JP) ; Ishiguro; Shigeki; (Osaka, JP) ; Yoshie;
Satomi; (Osaka, JP) ; Sekiguchi; Yuka; (Osaka,
JP) ; Hayashiuchi; Rie; (Osaka, JP) ; Endo;
Asuka; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NITTO DENKO CORPORATION |
Osaka |
|
JP |
|
|
Assignee: |
NITTO DENKO CORPORATION
Osaka
JP
|
Family ID: |
48947192 |
Appl. No.: |
14/377026 |
Filed: |
December 21, 2012 |
PCT Filed: |
December 21, 2012 |
PCT NO: |
PCT/JP2012/083227 |
371 Date: |
August 6, 2014 |
Current U.S.
Class: |
428/352 ;
264/175 |
Current CPC
Class: |
B29K 2995/0094 20130101;
B29K 2105/251 20130101; C08L 67/04 20130101; C09J 2467/005
20130101; B29K 2021/00 20130101; B29K 2027/18 20130101; B29K
2223/12 20130101; B29K 2096/02 20130101; Y10T 428/254 20150115;
B29K 2105/0067 20130101; C09J 2427/006 20130101; B29K 2025/06
20130101; B29K 2227/18 20130101; B29L 2007/008 20130101; B29C 43/52
20130101; B29K 2105/0088 20130101; C09J 2301/122 20200801; C09J
2467/006 20130101; B29C 43/24 20130101; C08J 5/18 20130101; C09J
2421/006 20130101; C08J 2367/04 20130101; C09J 7/25 20180101; B29L
2031/3468 20130101; C08L 51/06 20130101; B29K 2105/0005 20130101;
C09J 2451/006 20130101; Y10T 428/28 20150115; C09J 2423/106
20130101; B29K 2995/0041 20130101; B29K 2067/046 20130101; C08K
5/103 20130101; C09J 2301/302 20200801; C09J 2203/306 20130101;
Y10T 428/2839 20150115; B29K 2023/12 20130101; B29K 2033/12
20130101; C08K 5/103 20130101; C08L 67/04 20130101 |
Class at
Publication: |
428/352 ;
264/175 |
International
Class: |
C09J 7/02 20060101
C09J007/02; B29C 43/52 20060101 B29C043/52; B29C 43/24 20060101
B29C043/24 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2012 |
JP |
2012-027643 |
Feb 10, 2012 |
JP |
2012-027644 |
Feb 10, 2012 |
JP |
2012-027645 |
Claims
1. A separator comprising a separator substrate and a removable
pressure-sensitive adhesive layer on at least one surface of the
substrate, wherein the separator substrate is composed of a
polylactic acid film or sheet comprising polylactic acid (A),
wherein a tear strength (according to JIS K7128-3: Plastics--Film
and Sheeting--Determination of Tear Resistance, Part 3: Right
angled tear method) of the film or sheet is not less than 100 N/mm
when the film or sheet is torn at least in a flow direction
(machine direction: MD), the film or sheet stored under an
atmosphere at 100.degree. C. for 1 minute has a rate of dimensional
change due to heating of not more than .+-.3% in the flow direction
(MD) and a transverse direction (TD), the rate of dimensional
change due to heating being determined by Expression (1): rate of
dimensional change due to heating (%)=(L2-L1)/L1.times.100 (1)
where L1 represents a gauge length before a test, and L2 represents
a gauge length after the test, and the film or sheet stored under
an atmosphere at 100.degree. C. for 1 minute while a load of 300
g/mm.sup.2 is applied in the flow direction (MD) has a rate of
dimensional change due to loaded heating of not more than .+-.3% in
the flow direction (MD), the rate of dimensional change due to
loaded heating being determined by Expression (2) rate of
dimensional change due to loaded heating (%)=(L4-L3)/L3.times.100
(2) where L3 represents a gauge length before a test, and L4
represents a gauge length after the test.
2. The separator according to claim 1, wherein the polylactic acid
film or sheet included in the separator substrate further comprises
a reforming agent (E).
3. The separator according to claim 2, wherein the polylactic acid
film or sheet included in the separator substrate comprises
polyglycerol fatty acid ester and/or polyglycerol condensed hydroxy
fatty acid ester (a) as the reforming agent (E) such that the
weight ratio of the polylactic acid (A) to the polyglycerol fatty
acid ester and/or polyglycerol condensed hydroxy fatty acid ester
(a) is 99:1 to 80:20 ((A):total amount of (a)).
4. The separator according to claim 2, wherein the polylactic acid
film or sheet included in the separator substrate comprises a
core-shell-structured polymer (b) composed of a particulate rubber
and a graft layer formed on the outside of the rubber as the
reforming agent (E) such that the weight ratio of the polylactic
acid (A) to the core-shell-structured polymer (b) composed of a
particulate rubber and a graft layer formed on the outside of the
rubber is 99:1 to 80:20 ((A):(b)).
5. The separator according to claim 2, wherein the polylactic acid
film or sheet included in the separator substrate comprises a soft
aliphatic polyester (c) as the reforming agent (E) such that the
weight ratio of the polylactic acid (A) to the soft aliphatic
polyester (c) is 95:5 to 60:40 ((A):(c)).
6. The separator according to claim 1, wherein the polylactic acid
film or sheet included in the separator substrate further comprises
0.1 to 10 parts by weight of an acidic functional group-modified
olefin polymer (B) based on 100 parts by weight of the polylactic
acid (A) (or a composition comprising the polylactic acid (A) and
the reforming agent (E) when the reforming agent (E) is contained),
the acidic functional group-modified olefin polymer (B) having an
acid value of 10 to 70 mgKOH/g and a weight average molecular
weight of 10000 to 80000.
7. The separator according to claim 6, wherein the acidic
functional group of the acidic functional group-modified olefin
polymer (B) is an acid anhydride group.
8. The separator according to claim 1, wherein the polylactic acid
film or sheet included in the separator substrate further comprises
0.5 to 15 parts by weight of a fluorine-containing polymer (C)
based on 100 parts by weight of the polylactic acid (A) (or a
composition comprising the polylactic acid (A) and the reforming
agent (E) when the reforming agent (E) is contained).
9. The separator according to claim 8, wherein the
fluorine-containing polymer (C) is a tetrafluoroethylene
polymer.
10. The separator according to claim 1, wherein the polylactic acid
film or sheet included in the separator substrate further comprises
0.1 to 15 parts by weight of a crystallization promoter (D) based
on 100 parts by weight of the polylactic acid (A) (or a composition
comprising the polylactic acid (A) and the reforming agent (E) when
the reforming agent (E) is contained).
11. The separator according to claim 1, wherein the polylactic acid
film or sheet included in the separator substrate is a film or
sheet formed by a melt film forming method.
12. The separator according to claim 11, wherein the melt film
forming method is calendering.
13. A method of producing a separator including a separator
substrate composed of a polylactic acid film or sheet prepared by
forming a resin composition comprising polylactic acid (A) into a
film by a melt film forming method, the method comprising: a melt
film forming step of melt forming the resin composition, a cooling
solidifying step of cooling and solidifying the resin composition
after the melt film forming step to prepare a film or sheet, and a
crystallization promoting step of heating the film or sheet after
the cooling solidifying step to promote crystallization of the film
or sheet, wherein a resin temperature in the melt film forming step
is within the range of (Tm)-15.degree. C. to (Tm)+15.degree. C.
where Tm represents a melting temperature of the resin composition
during raising of temperature, and in at least part of the
crystallization promoting step, crystallization of the film or
sheet is promoted within the temperature range of (Tc)+10.degree.
C. to (Tc)+50.degree. C. where Tc represents a crystallization
temperature of the resin composition during the raising of
temperature.
14. The method of producing a separator according to claim 13,
further comprising a residual stress relaxing step after the melt
film forming step and before the cooling solidifying step, wherein
in the residual stress relaxing step, the resin composition is kept
within the temperature range of (Tm)-70.degree. C. to
(Tm)-20.degree. C.
15. The method of producing a separator according to claim 13,
wherein the resin composition further comprises a reforming agent
(E).
16. The method of producing a separator according to claim 15,
wherein the resin composition comprises polyglycerol fatty acid
ester and/or polyglycerol condensed hydroxy fatty acid ester (a) as
the reforming agent (E) such that the weight ratio of the
polylactic acid (A) to the polyglycerol fatty acid ester and/or
polyglycerol condensed hydroxy fatty acid ester (a) is 99:1 to
80:20 ((A):total amount of (a)).
17. The method of producing a separator according to claim 15,
wherein the resin composition comprises a core-shell-structured
polymer (b) composed of a particulate rubber and a graft layer
formed on the outside of the rubber as the reforming agent (E) such
that the weight ratio of the polylactic acid (A) to the
core-shell-structured polymer (b) composed of a particulate rubber
and a graft layer formed on the outside of the rubber is 99:1 to
80:20 ((A):(b)).
18. The method of producing a separator according to claim 15,
wherein the resin composition comprises a soft aliphatic polyester
(c) as the reforming agent (E) such that the weight ratio of the
polylactic acid (A) to the soft aliphatic polyester (c) is 95:5 to
60:40 ((A):(c)).
19. The method of producing a separator according to claim 13,
wherein the resin composition further comprises 0.1 to 10 parts by
weight of an acidic functional group-modified olefin polymer (B)
based on 100 parts by weight of the polylactic acid (A) (or a
composition comprising the polylactic acid (A) and the reforming
agent (E) when the reforming agent (E) is contained), the acidic
functional group-modified olefin polymer (B) having an acid value
of 10 to 70 mgKOH/g and a weight average molecular weight of 10000
to 80000.
20. The method of producing a separator according to claim 19,
wherein the acidic functional group of the acidic functional
group-modified olefin polymer (B) is an acid anhydride group.
21. The method of producing a separator according to claim 13,
wherein the resin composition further comprises 0.5 to 15 parts by
weight of a fluorine-containing polymer (C) based on 100 parts by
weight of the polylactic acid (A) (or a composition comprising the
polylactic acid (A) and the reforming agent (E) when the reforming
agent (E) is contained).
22. The method of producing a separator according to claim 21,
wherein the fluorine-containing polymer (C) is a
tetrafluoroethylene polymer.
23. The method of producing a separator according to claim 13,
wherein the resin composition further comprises 0.1 to 15 parts by
weight of a crystallization promoter (D) based on 100 parts by
weight of the polylactic acid (A) (or a composition comprising the
polylactic acid (A) and the reforming agent (E) when the reforming
agent (E) is contained).
24. The method of producing a separator according to claim 13,
wherein the melt film forming method is calendering.
Description
TECHNICAL FIELD
[0001] The present invention relates to a separator, and more
specifically relates to a separator (release liner) including a
substrate composed of a polylactic acid film or sheet that has high
heat resistance and high tear resistance, and does not break or
tear during production or processing. The separator is used to
protect surfaces of pressure-sensitive adhesive layers of
pressure-sensitive adhesive tapes, pressure-sensitive adhesive
sheets, labels, and the like.
BACKGROUND ART
[0002] Polylactic acid is a plant-derived biomass polymer, and has
been receiving attention as a resin alternative to
petroleum-derived polymers. Polylactic acid, which is a highly
elastic and strong polymer, unfortunately, lacks toughness and has
low impact resistance, low tear resistance, and low flexibility.
Polylactic acid has a low rate of crystallization, and barely shows
crystal growth in ordinary crystal growth. Although the melting
point is approximately 170.degree. C., polylactic acid thermally
deforms at temperatures of not less than the glass transition
temperature, i.e., not less than 60.degree. C., and cannot keep a
film shape. Then, to improve the heat resistance of polylactic acid
resin films, several methods have been heretofore suggested.
[0003] As the measures against these problems, a method of blending
polylactic acid with a soft and heat resistant polymer to improve
the heat resistance of a polylactic acid resin film has been
suggested (PTL 1). Alternatively, a method of adding aliphatic
polyester/core-shell type rubber to polylactic acid, and
monoaxially or biaxially drawing a film formed of the prepared
polylactic acid has been suggested (PTL 2). Both methods can attain
impact resistance and heat resistance at the same time.
Unfortunately, blending of large amounts of the petroleum-derived
polymer and additives significantly reduces the ratio of the
plant-derived component (degree of biomass).
[0004] A technique of giving flexibility and heat resistance to a
polylactic acid film has been suggested, in which crystallization
of a resin composition comprising polylactic acid, a plasticizer,
and a nucleator is promoted in a heat treatment step subsequent to
a step of molding a film (PTL 3). Unfortunately, in this method,
addition of the plasticizer may cause bleed-out, and an effect of
improving tear resistance is little while an effect of improving
flexibility is attained. If such a film or sheet is used as a
substrate for a separator, such separator may be broken or torn
during the production or processing thereof.
CITATION LIST
Patent Literature
[0005] PTL 1: Japanese Patent Laid-Open No. 2006-70224
[0006] PTL 2: Japanese Patent Laid-Open No. 2009-173715
[0007] PTL 3: Japanese Patent No. 4699180
SUMMARY OF INVENTION
Technical Problem
[0008] Then, an object of the present invention is to provide a
separator including a substrate composed of a polylactic acid film
or sheet having tear strength so as not to break or tear during,
for example, production or processing of the separator or winding
thereof into a roll, and causing neither melt nor deformation at
high temperatures more than 100.degree. C.
Solution to Problem
[0009] The present inventors, who have conducted extensive research
to attain the above objects, found that the problems above can be
solved by use of, as a separator substrate, a polylactic acid resin
film or sheet having a tear strength of not less than a
predetermined value and having a rate of dimensional change due to
heating (%) of not more than a predetermined value and a rate of
dimensional change due to loaded heating (%) of not more than a
predetermined value, and have completed the present invention.
[0010] Namely, the present invention provides
[0011] a separator comprising a separator substrate and a removable
pressure-sensitive adhesive layer on at least one surface of the
substrate,
[0012] wherein the separator substrate is composed of a polylactic
acid film or sheet comprising
[0013] polylactic acid (A),
[0014] wherein a tear strength (according to JIS K7128-3:
Plastics--Film and Sheeting--Determination of Tear Resistance, Part
3: Right angled tear method) of the film or sheet is not less than
100 N/mm when the film or sheet is torn at least in a flow
direction (machine direction: MD),
[0015] the film or sheet stored under an atmosphere at 100.degree.
C. for 1 minute has a rate of dimensional change due to heating of
not more than .+-.3% in the flow direction (MD) and a transverse
direction (TD), the rate of dimensional change due to heating being
determined by Expression (1):
rate of dimensional change due to heating (%)=(L2-L1)/L1.times.100
(1)
where L1 represents a gauge length before a test, and L2 represents
a gauge length after the test, and
[0016] the film or sheet stored under an atmosphere at 100.degree.
C. for 1 minute while a load of 300 g/mm.sup.2 is applied in the
flow direction (MD) has a rate of dimensional change due to loaded
heating of not more than .+-.3% in the flow direction (MD), the
rate of dimensional change due to loaded heating being determined
by Expression (2)
rate of dimensional change due to loaded heating
(%)=(L4-L3)/L3.times.100 (2)
where L3 represents a gauge length before a test, and L4 represents
a gauge length after the test.
[0017] The polylactic acid film or sheet included in the separator
substrate may further comprise a reforming agent (E). The
polylactic acid film or sheet included in the separator substrate
may comprise a polyglycerol fatty acid ester and/or polyglycerol
condensed hydroxy fatty acid ester (a) as the reforming agent (E)
such that the weight ratio of the polylactic acid (A) to the
polyglycerol fatty acid ester and/or polyglycerol condensed hydroxy
fatty acid ester (a) is 99:1 to 80:20 ((A):total amount of
(a)).
[0018] The polylactic acid film or sheet included in the separator
substrate may comprise a core-shell-structured polymer (b) composed
of a particulate rubber and a graft layer formed on the outside of
the rubber as the reforming agent (E) such that the weight ratio of
the polylactic acid (A) to the core-shell-structured polymer (b)
composed of a particulate rubber and a graft layer formed on the
outside of the rubber is 99:1 to 80:20 ((A):(b)).
[0019] The polylactic acid film or sheet included in the separator
substrate may comprise a soft aliphatic polyester (c) as the
reforming agent (E) such that the weight ratio of the polylactic
acid (A) to the soft aliphatic polyester (c) is 95:5 to 60:40
((A):(c)).
[0020] The polylactic acid film or sheet included in the separator
substrate may further comprise 0.1 to 10 parts by weight of an
acidic functional group-modified olefin polymer (B) based on 100
parts by weight of the polylactic acid (A) (or a composition
comprising the polylactic acid (A) and the reforming agent (E) when
the reforming agent (E) is contained), the acidic functional
group-modified olefin polymer (B) having an acid value of 10 to 70
mgKOH/g and a weight average molecular weight of 10000 to 80000.
The acidic functional group of the acidic functional group-modified
olefin polymer (B) may be an acid anhydride group.
[0021] The polylactic acid film or sheet included in the separator
substrate may further comprise 0.5 to 15 parts by weight of a
fluorine-containing polymer (C) based on 100 parts by weight of the
polylactic acid (A) (or a composition comprising the polylactic
acid (A) and the reforming agent (E) when the reforming agent (E)
is contained). The fluorine-containing polymer (C) may be a
tetrafluoroethylene polymer.
[0022] The polylactic acid film or sheet included in the separator
substrate may further comprise 0.1 to 15 parts by weight of a
crystallization promoter (D) based on 100 parts by weight of the
polylactic acid (A) (or a composition comprising the polylactic
acid (A) and the reforming agent (E) when the reforming agent (E)
is contained).
[0023] The polylactic acid film or sheet included in the separator
substrate may be a film or sheet formed by a melt film forming
method such as calendering.
[0024] The present invention provides
[0025] a method of producing a separator including a separator
substrate composed of a polylactic acid film or sheet prepared by
forming a resin composition comprising polylactic acid (A) into a
film by a melt film forming method, the method comprising:
[0026] a melt film forming step of melt forming the resin
composition,
[0027] a cooling solidifying step of cooling and solidifying the
resin composition after the melt film forming step to prepare a
film or sheet, and
[0028] a crystallization promoting step of heating the film or
sheet after the cooling solidifying step to promote crystallization
of the film or sheet,
[0029] wherein a resin temperature in the melt film forming step is
within the range of (Tm)-15.degree. C. to (Tm)+15.degree. C. where
Tm represents a melting temperature of the resin composition during
raising of temperature, and
[0030] in at least part of the crystallization promoting step,
crystallization of the film or sheet is promoted within the
temperature range of (Tc)+10.degree. C. to (Tc)+50.degree. C. where
Tc represents a crystallization temperature of the resin
composition during the raising of temperature.
[0031] The method of producing a separator may comprise
[0032] a residual stress relaxing step after the melt film forming
step and before the cooling solidifying step,
[0033] wherein in the residual stress relaxing step, the resin
composition may be kept within the temperature range of
(Tm)-70.degree. C. to (Tm)-20.degree. C.
[0034] The resin composition may further comprise a reforming agent
(E).
[0035] The resin composition may comprise polyglycerol fatty acid
ester and/or polyglycerol condensed hydroxy fatty acid ester (a) as
the reforming agent (E) such that the weight ratio of the
polylactic acid (A) to the polyglycerol fatty acid ester and/or
polyglycerol condensed hydroxy fatty acid ester (a) is 99:1 to
80:20 ((A):total amount of (a)).
[0036] The resin composition may comprise a core-shell-structured
polymer (b) composed of a particulate rubber and a graft layer
formed on the outside of the rubber as the reforming agent (E) such
that the weight ratio of the polylactic acid (A) to the
core-shell-structured polymer (b) composed of a particulate rubber
and a graft layer formed on the outside of the rubber is 99:1 to
80:20 ((A):(b)).
[0037] The resin composition may comprise a soft aliphatic
polyester (c) as the reforming agent (E) such that the weight ratio
of the polylactic acid (A) to the soft aliphatic polyester (c) is
95:5 to 60:40 ((A):(c)).
[0038] The resin composition may further comprise 0.1 to 10 parts
by weight of an acidic functional group-modified olefin polymer (B)
based on 100 parts by weight of the polylactic acid (A) (or a
composition comprising the polylactic acid (A) and the reforming
agent (E) when the reforming agent (E) is contained), the acidic
functional group-modified olefin polymer (B) having an acid value
of 10 to 70 mgKOH/g and a weight average molecular weight of 10000
to 80000. The acidic functional group of the acidic functional
group-modified olefin polymer (B) may be an acid anhydride
group.
[0039] The resin composition may further comprise 0.5 to 15 parts
by weight of a fluorine-containing polymer (C) based on 100 parts
by weight of the polylactic acid (A) (or a composition comprising
the polylactic acid (A) and the reforming agent (E) when the
reforming agent (E) is contained). The fluorine-containing polymer
(C) may be a tetrafluoroethylene polymer.
[0040] The resin composition may further comprise 0.1 to 15 parts
by weight of a crystallization promoter (D) based on 100 parts by
weight of the polylactic acid (A) (or a composition comprising the
polylactic acid (A) and the reforming agent (E) when the reforming
agent (E) is contained).
[0041] The melt film forming method may be calendering.
Advantageous Effects of Invention
[0042] The substrate for the separator according to the present
invention does not melt or deform at high temperatures more than
100.degree. C. The substrate keeps its intrinsic rigidity and does
not break or tear when tension is applied to the substrate during,
for example, production or processing of the separator or winding
thereof into a roll.
BRIEF DESCRIPTION OF DRAWINGS
[0043] FIG. 1 is a schematic view of an example of a calendering
film forming machine used in production of a separator substrate
(polylactic acid film or sheet) for the separator according to the
present invention.
[0044] FIG. 2 is a schematic view showing an example of a polishing
film forming machine used in production of the separator substrate
(polylactic acid film or sheet) for the separator according to the
present invention.
DESCRIPTION OF EMBODIMENTS
[Separator Substrate]
[0045] The polylactic acid film or sheet used as a substrate for a
separator (separator substrate) according to the present invention
is a resin film or sheet comprising polylactic acid (A). The raw
material monomer for polylactic acid, lactic acid, has asymmetric
carbon atoms, and has optical isomers of L-form and D-form.
Polylactic acid (A) used in the present invention is a polymer
including L-form lactic acid as the main component. As a smaller
content of D-form lactic acid is mixed as impurities during
production, the resultant polymer has higher crystallinity and a
higher melting point. A raw material having high purity of L-form
is preferably used, and those having a purity of L-form of not less
than 95% are more preferably used. Polylactic acid (A) may contain
other copolymerization components in addition to lactic acid.
[0046] Examples of the other copolymerization components include
polyol compounds such as ethylene glycol, propylene glycol,
1,3-propanediol, butanediol, pentanediol, neopentyl glycol,
hexanediol, heptanediol, octanediol, nonanediol, decanediol,
1,4-cyclohexanedimethanol, glycerol, pentaerythritol, polyethylene
glycol, polypropylene glycol, polytetramethylene glycol, and
bisphenol A; polyvalent carboxylic acids such as oxalic acid,
malonic acid, glutaric acid, adipic acid, sebacic acid, azelaic
acid, dodecanedione acid, cyclohexanedicarboxylic acid,
terephthalic acid, isophthalic acid, phthalic acid,
naphthalenedicarboxylic acid, bis(p-carboxyphenyl)methane,
anthracenedicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid,
5-sodiumsulfoisophthalic acid, and
5-tetrabutylphosphoniumisophthalic acid; hydroxycarboxylic acids
such as glycolic acid, hydroxypropionic acid, hydroxybutyric acid,
hydroxyvaleric acid, hydroxycaproic acid, and hydroxybenzoic acid;
and lactones such as propiolactone, valerolactone, caprolactone,
undecalactone, and 1,5-oxepan-2-one. These copolymerization
components are contained in a proportion of preferably 0 to 30 mol
%, more preferably 0 to 10 mol % based on the total monomer
components that form the polylactic acid (A).
[0047] The weight average molecular weight of the polylactic acid
(A) is, for example, 10000 to 400000, preferably 50000 to 300000,
more preferably 80000 to 200000. The melt flow rate [JIS K-7210
(test condition 4)] of the polylactic acid (A) at 190.degree. C.
and a load of 21.2 N is, for example, 0.1 to 50 g/10 min,
preferably 0.2 to 20 g/10 min, more preferably 0.5 to 10 g/10 min,
particularly preferably 1 to 7 g/10 min. An excessively high value
of the melt flow rate may reduce the mechanical properties and heat
resistance of the prepared film or sheet. An excessively low value
of the melt flow rate may excessively increase load during film
formation.
[0048] In the present invention, the "weight average molecular
weight" refers to the value measured by gel permeation
chromatography (GPC) (in terms of polystyrene). The measurement
conditions for GPC are as follows:
[0049] column: TSKgel SuperHZM-H/HZ2000/HZ1000
[0050] column size: 4.6 mmI.D..times.150 mm
[0051] eluent: chloroform
[0052] flow rate: 0.3 ml/min
[0053] detector: RI
[0054] column temperature: 40.degree. C.
[0055] amount of injection: 10 .mu.l
[0056] Polylactic acid can be prepared by any method.
Representative examples of the production method include
lactidation and direct polymerization. Lactidation is a method for
preparing high molecular weight polylactic acid in which lactic
acid is heated and dehydration condensed to prepare low molecular
weight polylactic acid; the low molecular weight polylactic acid is
pyrolyzed under reduced pressure to prepare a cyclic dimer of
lactic acid, lactide; and the lactide is subjected to ring-opening
polymerization in the presence of a metal salt catalyst such as
tin(II) octanoate. Direct polymerization is a method for directly
preparing polylactic acid in which lactic acid is heated in a
solvent such as diphenyl ether under reduced pressure to be
polymerized while the moisture content is being removed to suppress
hydrolysis.
[0057] Commercially available products can be used as the
polylactic acid (A). Examples of commercially available products
include trade names "LACEA H-400" and "LACEA H-100" (made by Mitsui
Chemicals, Inc.), and trade names "Terramac TP-4000" and "Terramac
TE-4000" (made by Unitika Limited). Any polylactic acid (A)
prepared by a known standard polymerization method (such as
emulsion polymerization and solution polymerization) can be
used.
[0058] The content of the polylactic acid (A) in the polylactic
acid film or sheet is usually not less than 60% by weight,
preferably not less than 70% by weight, more preferably not less
than 80% by weight, particularly preferably not less than 85% by
weight from the viewpoint of increase in the degree of biomass. The
upper limit of the content of the polylactic acid (A) is, for
example, 97% by weight, preferably 95% by weight, more preferably
93% by weight. Herein, the degree of biomass refers to the
proportion of the dry weight of biomass used to the dry weight of
the film or sheet. Biomass refers to regenerative organic resources
derived from living organisms excluding fossil resources.
[0059] In the present invention, the polylactic acid film or sheet
used to form a separator substrate may comprise an acidic
functional group-modified olefin polymer (B). The acidic functional
group-modified olefin polymer (B) compounded with the polylactic
acid (A) can give rolling lubrication. This property enables the
polylactic acid film or sheet to readily remove from the surfaces
of metal rolls when the polylactic acid film or sheet is melt with
a calendering film forming machine or the like and passed through
between the metal rolls, leading to smooth film formation. These
acidic functional group-modified olefin polymers (B) may be used
singly or in combinations of two or more.
[0060] Examples of the acidic functional group of the acidic
functional group-modified olefin polymer (B) include a carboxyl
group or derivative groups thereof. Examples of the derivative
groups of the carboxyl group include groups chemically derived from
a carboxyl group such as acid anhydride groups, ester groups, amide
groups, imide groups, and cyano groups of carboxylic acid. Among
these, carboxylic anhydride groups are preferable.
[0061] The acidic functional group-modified olefin polymer (B) is
prepared by grafting an unsaturated compound containing the "acidic
functional group" (hereinafter abbreviated to "acidic functional
group-containing unsaturated compound" in some cases) to an
unmodified polyolefin polymer.
[0062] Examples of the unmodified polyolefin polymer include
polyolefins, such as high density polyethylene, middle density
polyethylene, low density polyethylene, polypropylene, polybutene,
poly-4-methylpentene-1, copolymers of ethylene and .alpha.-olefin,
and copolymers of propylene and .alpha.-olefin, or oligomers
thereof; polyolefin elastomers, such as ethylene-propylene rubbers,
ethylene-propylene-diene copolymer rubbers, butyl rubbers,
butadiene rubbers, low crystalline ethylene-propylene copolymers,
propylene-butene copolymers, ethylene-vinyl ester copolymers,
ethylene-methyl (meth)acrylate copolymers,
ethylene-ethyl(meth)acrylate copolymers, ethylene-maleic anhydride
copolymers, and blends of polypropylene and ethylene-propylene
rubbers; and mixtures thereof. Among these, polypropylene,
copolymers of propylene and .alpha.-olefin, low density
polyethylene, and oligomers thereof are preferable, and
polypropylene, copolymers of propylene and .alpha.-olefin, and
oligomers thereof are particularly preferable. Examples of the
"oligomers" include those prepared from the corresponding polymers
by a molecular weight degradation method using pyrolysis. The
oligomers can also be prepared by polymerization.
[0063] Examples of the acidic functional group-containing
unsaturated compound include carboxyl group-containing unsaturated
compounds and unsaturated compounds containing derivative groups of
a carboxyl group. Examples of the carboxyl group-containing
unsaturated compound include maleic acid, itaconic acid,
chloroitaconic acid, chloromaleic acid, citraconic acid, and
(meth)acrylic acid. Examples of unsaturated compounds containing
derivative groups of a carboxyl group include carboxylic anhydride
group-containing unsaturated compounds such as maleic anhydride,
itaconic anhydride, chloroitaconic anhydride, chloromaleic
anhydride, and citraconic anhydride; (meth)acrylates such as
methyl(meth)acrylate, glycidyl(meth)acrylate, and
2-hydroxyethyl(meth)acrylate; and (meth)acrylamide, maleimide, and
(meth)acrylonitrile. Among these, the carboxyl group-containing
unsaturated compounds and the carboxylic anhydride group-containing
unsaturated compounds are preferable, acid anhydride
group-containing unsaturated compounds are more preferable, and
maleic anhydride is particularly preferable.
[0064] It is important that the weight average molecular weight of
the acidic functional group-modified olefin polymer (B) is 10000 to
80000, preferably 15000 to 70000, more preferably 20000 to 60000. A
weight average molecular weight less than 10000 will cause
bleed-out after molding of the film or sheet while a weight average
molecular weight more than 80000 will cause the polymer (B) to
separate from the polylactic acid (A) during roll kneading. Herein,
bleed-out refers to a phenomenon in which a low molecular weight
component comes out of the surface of the film or sheet after
molding of the film or sheet as the time passes.
[0065] The acidic functional group in the acidic functional
group-modified olefin polymer (B) may modify in any modified
proportion or bond to any position of the olefin polymer. The acid
value of the acidic functional group-modified olefin polymer (B) is
usually 10 to 70 mgKOH/g, preferably 20 to 60 mgKOH/g. An acid
value less than 10 mgKOH/g cannot attain the effect of improving
rolling lubrication while an acid value more than 70 mgKOH/g will
cause plate out to the roll. Herein, the plate out to the roll
refers to a phenomenon in which during melt film forming of a resin
composition using a metal roll, components compounded with the
resin composition or oxidized, decomposed, combined, or degraded
products thereof, etc. adhere to or deposit on the surface of the
metal roll. In the present invention, the "acid value" refers to
the value measured according to JIS K0070-1992: Neutralization
Titration.
[0066] The acidic functional group-modified olefin polymer (B) is
prepared by reacting the unmodified polyolefin polymer with the
acidic functional group-containing unsaturated compound in the
presence of an organic peroxide. Any organic peroxide used as a
standard initiator in radical polymerization can be used. The
reaction can be performed by any of a solution method and a melting
method. In the solution method, the acidic functional
group-modified olefin polymer (B) can be prepared by dissolving a
mixture of the unmodified polyolefin polymer and the acidic
functional group-containing unsaturated compound with an organic
peroxide in an organic solvent, and heating the mixture. The
reaction temperature is preferably approximately 110 to 170.degree.
C.
[0067] In the melting method, the acidic functional group-modified
olefin polymer (B) can be prepared by mixing a mixture of the
unmodified polyolefin polymer and the acidic functional
group-containing unsaturated compound with an organic peroxide, and
reacting the mixture by melt mixing. Melt mixing can be performed
with a variety of mixers such as extruders, Brabenders, kneaders,
and Banbury mixers. The kneading temperature is usually within the
temperature range of the melting point of the unmodified polyolefin
polymer to 300.degree. C.
[0068] The acidic functional group-modified olefin polymer (B) is
preferably maleic anhydride modified polypropylene. Commercially
available products can be used as the acidic functional
group-modified olefin polymer (B), and examples thereof include
trade names "Umex 1010" (maleic anhydride group-modified
polypropylene, acid value: 52 mgKOH/g, weight average molecular
weight: 32000, modified proportion: 10% by weight), "Umex 1001"
(maleic anhydride group-modified polypropylene, acid value: 26
mgKOH/g, weight average molecular weight: 49000, modified
proportion: 5% by weight), "Umex 2000" (maleic anhydride
group-containing modified polyethylene, acid value: 30 mgKOH/g,
weight average molecular weight: 20000, modified proportion: 5% by
weight) made by Sanyo Chemical Industries, Ltd.
[0069] The acidic functional group-modified olefin polymer (B) in
the polylactic acid film or sheet can be used in any content. For
example, 0.1 to 10 parts by weight of the acidic functional
group-modified olefin polymer (B) having an acid value of 10 to 70
mgKOH/g and a weight average molecular weight of 10000 to 80000 may
be contained based on 100 parts by weight of the polylactic acid
(A) (or a composition comprising the polylactic acid (A) and the
reforming agent (E) when the reforming agent (E) is contained). The
content thereof is preferably 0.1 to 5 parts by weight,
particularly preferably 0.3 to 3 parts by weight from the viewpoint
of maintenance of the effect of rolling lubrication without plate
out to the roll and maintenance of the degree of biomass. Less than
0.1 parts by weight of the acidic functional group-modified olefin
polymer (B) is difficult to attain the effect of improving rolling
lubrication while more than 10 parts by weight of the acidic
functional group-modified olefin polymer (B) cannot attain the
effect according to the amount of addition, and reduces the degree
of biomass.
[0070] In the present invention, the polylactic acid film or sheet
used to form the separator substrate may contain a
fluorine-containing polymer (C) in addition to the components
above. The fluorine-containing polymer (C) is used as a melt
tension adjuster or a crystallization promoter, for example.
Examples of the fluorine-containing polymer (C) include
tetrafluoroethylene polymers, polychlorotrifluoroethylene,
polyvinylidene fluoride, and polyvinyl fluoride. These
fluorine-containing polymers (C) may be used singly or in
combinations of two or more. Particularly, tetrafluoroethylene
polymer (C') can be suitably used as the fluorine-containing
polymer (C).
[0071] The tetrafluoroethylene polymer (C') may be a homopolymer of
tetrafluoroethylene or a copolymer of tetrafluoroethylene and an
additional monomer. Examples of the tetrafluoroethylene polymer
(C') include polytetrafluoroethylene, perfluoroalkoxyalkane
(copolymers of tetrafluoroethylene and perfluoroalkylvinylether),
perfluoroethylene propene copolymers (copolymers of
tetrafluoroethylene and hexafluoropropylene),
ethylene-tetrafluoroethylene copolymers, and
tetrafluoroethylene-perfluorodioxol copolymers. Among these,
polytetrafluoroethylene is preferable. These tetrafluoroethylene
polymers (C') may be used singly or in combinations of two or
more.
[0072] If the fluorine-containing polymer (C) is compounded with
the polylactic acid (A)-containing resin composition, melt tension
is improved and melt viscosity is increased. For example, in film
formation with a calender roll, these properties can prevent
elongation and peel-off failure, which might be caused when the
resin composition formed into a film is removed from the roll.
Particularly, fluorine-containing polymers such as the
tetrafluoroethylene polymer (C') serve as a nucleator for the
polylactic acid (A). Such polymers can further promote
crystallization of the polylactic acid (A) by setting the
temperature of the resin composition immediately after film
formation at a temperature close to the crystallization temperature
thereof. As above, the fluorine-containing polymer (C)
[particularly tetrafluoroethylene polymer (C')] compounded can
promote crystallization of the polylactic acid (A), enhancing
.DELTA.Hc' of the polylactic acid film or sheet.
[0073] It seems that the action as a nucleator of the
tetrafluoroethylene polymer (C') on the polylactic acid (A) depends
on the crystal structure of the tetrafluoroethylene polymer (C').
According to the determination by wide angle X ray diffraction, the
crystal lattice of polylactic acid had a plane interval of 4.8
angstroms while tetrafluoroethylene polymer (C') had a plane
interval of 4.9 angstroms. From this, it is considered that the
tetrafluoroethylene polymer (C') has an epitaxy effect, and can
serve as a nucleator for the polylactic acid (A). Herein, the
epitaxy effect refers to a manner of growth in which the polylactic
acid (A) crystal grows on the surface of the tetrafluoroethylene
polymer (C') to align the polylactic acid (A) along the crystal
planes on the crystal surface of the tetrafluoroethylene polymer
(C').
[0074] The plane interval of the tetrafluoroethylene polymer (C')
and that of a copolymer of tetrafluoroethylene and an additional
monomer both are governed by the form of crystal of a
tetrafluoroethylene portion, and the plane intervals thereof are
the same. Accordingly, the copolymer can contain the additional
monomer component in any content to the extent that the form of
crystal of polytetrafluoroethylene can be kept and physical
properties do not change much. Desirably, the proportion of the
additional monomer component in the tetrafluoroethylene polymer
(C') is usually not more than 5% by weight.
[0075] The tetrafluoroethylene polymer (C') can be prepared by any
polymerization method, and those prepared by emulsion
polymerization are particularly preferable. The tetrafluoroethylene
polymer prepared by emulsion polymerization readily turns into
fibers to have a network structure in the polylactic acid (A). This
structure probably effectively serves to improve the melt tension
of the resin composition containing the polylactic acid (A).
[0076] To uniformly disperse the tetrafluoroethylene polymer (C')
in the polylactic acid (A), particles of the tetrafluoroethylene
polymer (C') modified with a polymer having good affinity with the
polylactic acid (A), such as a (meth)acrylate polymer, may be used.
Examples of such a tetrafluoroethylene polymer (C') include
acrylic-modified polytetrafluoroethylene.
[0077] The fluorine-containing polymer (C) [such as the
tetrafluoroethylene polymer (C')] can have any weight average
molecular weight. The weight average molecular weight is usually
1000000 to 10000000, preferably 2000000 to 8000000.
[0078] Commercially available products may be used as the
fluorine-containing polymer (C) [such as the tetrafluoroethylene
polymer (C')]. Examples of commercially available products of
polytetrafluoroethylene include trade names "Fluon CD-014," "Fluon
CD-1," and "Fluon CD-145" made by ASAHI GLASS CO., LTD. Examples of
commercially available products of acrylic-modified
polytetrafluoroethylene include METABLEN A series such as trade
names "METABLEN A-3000" and "METABLEN A-3800" made by MITSUBISHI
RAYON CO., LTD.
[0079] The polylactic acid film or sheet can contain the
fluorine-containing polymer (C) [particularly, the
tetrafluoroethylene polymer (C')] in any content. For example, the
polylactic acid film or sheet can contain 0.5 to 15 parts by weight
of the fluorine-containing polymer (C) based on 100 parts by weight
of the polylactic acid (A) (or a composition comprising the
polylactic acid (A) and the reforming agent (E) when the reforming
agent (E) is contained). The content of the fluorine-containing
polymer (C) is preferably 0.7 to 10 parts by weight, more
preferably 1 to 5 parts by weight from the viewpoint of the effect
of improving melt tension, maintenance of the degree of biomass,
and achievement of a good surface state. If the content of the
fluorine-containing polymer (C) [particularly, content of the
tetrafluoroethylene polymer (C')] is less than 0.5 parts by weight,
the effect of improving melt tension is difficult to attain. If the
content is more than 15 parts by weight, the effect according to
the amount of addition cannot be attained, and the degree of
biomass reduces.
[0080] The polylactic acid film or sheet can be produced by any
specific method, and examples thereof include (1) forming the resin
composition containing the polylactic acid (A) into a film by a
melt film forming method such as calendering film formation, (2)
forming a resin composition comprising the polylactic acid (A) and
a crystallization promoter into a film, and (3) a combination
thereof. The melt film forming method will be described later.
[0081] The crystallization promoter other than the
fluorine-containing polymer usable as the crystallization promoter
[such as the tetrafluoroethylene polymer (C')] among the
fluorine-containing polymers (C) can be used as the crystallization
promoter. Such a crystallization promoter [referred to as
crystallization promoter (D) in some cases] can be used without
limitation as long as it is found to have the effect of promoting
crystallization. Desirably, a substance having a crystal structure
with a plane interval close to the plane interval of the crystal
lattice of the polylactic acid (A) is selected. This is because as
the plane interval of the crystal lattice of the substance is
closer to the plane interval of the crystal lattice of the
polylactic acid (A), the substance has a high effect as the
nucleator for the polylactic acid (A). Examples of such a
crystallization promoter (D) include organic substances such as
polyphosphoric acid melamine, melamine cyanurate, zinc phenyl
phosphonate, calcium phenyl phosphonate, and magnesium phenyl
phosphonate; and inorganic substances such as talc and clay. Among
these, zinc phenyl phosphonate is preferable because this substance
has a plane interval closest to the plane interval of the
polylactic acid (A) to attain a good effect of promoting
crystallization. These crystallization promoters (D) may be used
singly or in combinations of two or more.
[0082] Commercially available products can be used as the
crystallization promoter (D). Examples of commercially available
products of zinc phenyl phosphonate include trade name "ECOPROMOTE"
made by Nissan Chemical Industries, Ltd.
[0083] The polylactic acid film or sheet can contain the
crystallization promoter (D) in any content. For example, the
polylactic acid film or sheet contains 0.1 to 15 parts by weight of
the crystallization promoter (D) based on 100 parts by weight of
the polylactic acid (A) (or a composition comprising the polylactic
acid (A) and the reforming agent (E) when the reforming agent (E)
is contained). The content is preferably 0.3 to 10 parts by weight
from the viewpoint of a high effect of promoting crystallization
and maintenance of the degree of biomass. At a content of the
crystallization promoter (D) less than 0.1 parts by weight, the
effect of promoting crystallization is difficult to attain. At a
content more than 15 parts by weight, the effect according to the
amount of addition cannot be attained, and the degree of biomass
reduces. When 0.1 to 15 parts by weight of the tetrafluoroethylene
polymer (C') as the fluorine-containing polymer (C) is used based
on 100 parts by weight of the polylactic acid (A) (or a composition
comprising the polylactic acid (A) and the reforming agent (E) when
the reforming agent (E) is contained), the content of the
crystallization promoter (D) is preferably 0.1 to 5 parts by
weight, more preferably 0.3 to 3 parts by weight based on 100 parts
by weight of the polylactic acid (A) (or a composition comprising
the polylactic acid (A) and the reforming agent (E) when the
reforming agent (E) is contained) from the viewpoint of a high
effect of promoting crystallization and maintenance of the degree
of biomass. In this case, at a content of the crystallization
promoter (D) less than 0.1 parts by weight, the effect of promoting
crystallization is difficult to attain. At a content more than 5
parts by weight, the effect according to the amount of addition
cannot be attained, and the degree of biomass reduces.
[0084] In the present invention, the polylactic acid film or sheet
has a tear strength of not less than 100 N/mm, preferably not less
than 150 N/mm when the film or sheet is torn at least in the flow
direction (MD). If the polylactic acid film or sheet having such a
tear strength is used as the substrate for the separator, the
substrate does not break or tear during producing or processing the
separator including a step of applying tension. The substrate does
not break or tear during winding of the separator into a roll or a
process such punching.
[0085] In the present invention, the tear strength can be
determined according to JIS K7128-3: Plastics--Film and
Sheeting--Determination of Tear Resistance, Part 3: Right angled
tear method. As described above, the polylactic acid film or sheet
having a tear strength of not less than 100 N/mm when the film or
sheet is torn at least in the flow direction (MD) does not break or
tear not only during production of the film or sheet but also
during winding thereof into a roll or processing thereof. This
property enables various processes, widening its application range
significantly.
[0086] In the present invention, the polylactic acid film or sheet
has a rate of dimensional change due to heating of not more than
.+-.3%, preferably not more than .+-.2%, not more than .+-.1% in
the flow direction (MD) and the transverse direction (TD). When the
polylactic acid film or sheet having such a rate of dimensional
change due to heating is used as the substrate for the separator,
the film or sheet does not melt or deform under high temperature
conditions more than 100.degree. C., for example, and can be
sufficiently used in applications requiring heat resistance.
[0087] In the present invention, when the film or sheet is stored
under an atmosphere at 100.degree. C. for 1 minute, the rate of
dimensional change due to heating is determined by Expression
(1):
rate of dimensional change due to heating (%)=(L2-L1)/L1.times.100
(1)
where L1 represents a gauge length before a test, and L2 represents
a gauge length after the test.
[0088] In the present invention, the polylactic acid film or sheet
has a rate of dimensional change due to loaded heating of not more
than .+-.3%, preferably not more than .+-.2%, not more than .+-.1%
in the flow direction (MD) and the transverse direction (TD). When
the polylactic acid film or sheet having such a rate of dimensional
change due to loaded heating is used as the substrate for the
separator, the film or sheet does not melt or deform under high
temperature conditions of more than 100.degree. C., for example,
and can be sufficiently used in applications requiring heat
resistance.
[0089] In the present invention, when the film or sheet is stored
under an atmosphere at 100.degree. C. for 1 minute while a load of
300 g/mm.sup.2 is applied in the flow direction (MD), the rate of
dimensional change due to loaded heating is determined by
Expression (2):
rate of dimensional change due to loaded heating
(%)=(L4-L3)/L3.times.100 (2)
where L3 represents a gauge length before a test, and L4 represents
a gauge length after the test.
[0090] In the present invention, examples of a specific method for
further improving physical properties of the polylactic acid film
or sheet include a method of compounding the reforming agent (E)
with the polylactic acid (A) to prepare a resin composition and
forming the resin composition into a film.
[0091] Examples of the reforming agent (E) include polyglycerol
fatty acid esters or polyglycerol condensed hydroxy fatty acid
esters (a), core-shell-structured polymers (b) composed of a
particulate rubber and a graft layer formed on the outside of the
rubber, and soft aliphatic polyesters (c). These may be each used
singly or in combinations of two or more.
[0092] In the present invention, the polylactic acid film or sheet
contains the polyglycerol fatty acid ester and/or polyglycerol
condensed hydroxy fatty acid ester (a) as the reforming agent (E)
such that the weight ratio of the polylactic acid (A) to the
polyglycerol fatty acid ester and/or polyglycerol condensed hydroxy
fatty acid ester (a) is preferably 99:1 to 80:20 ((A):total amount
of (a)), more preferably 95:5 to 90:10 ((A):total amount of (a)).
These polyglycerol fatty acid esters and polyglycerol condensed
hydroxy fatty acid esters may be each used singly or in
combinations of two or more.
[0093] An excessively small amount of the polyglycerol fatty acid
ester and/or polyglycerol condensed hydroxy fatty acid ester (a)
leads to an insufficient effect of reforming physical properties.
An excessively large amount of the polyglycerol fatty acid ester
and/or polyglycerol condensed hydroxy fatty acid ester (a) readily
reduces the degree of crystallization and the rate of
crystallization, and may cause the polyglycerol fatty acid ester
and/or polyglycerol condensed hydroxy fatty acid ester (a) to bleed
out. When the polylactic acid film or sheet containing the
polyglycerol fatty acid ester or polyglycerol condensed hydroxy
fatty acid ester (a) in the above range is used as the substrate
for the separator, tear resistance can be improved without reducing
heat resistance.
[0094] In the polyglycerol fatty acid ester or polyglycerol
condensed hydroxy fatty acid ester (a), polyglycerol fatty acid
ester is prepared by a reaction of polyglycerol with fatty acid.
Examples of the constituent of the polyglycerol fatty acid ester,
i.e., polyglycerol, include diglycerol, triglycerol, tetraglycerol,
pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol,
nonaglycerol, decaglycerol, and dodecaglycerol. These are used
singly or as a mixture. The average degree of polymerization of
polyglycerol is preferably 2 to 10.
[0095] For the other constituent of the polyglycerol fatty acid
ester, i.e., fatty acid, fatty acids having not less than 12 carbon
atoms are used, for example. Specific examples of the fatty acids
include lauric acid, myristic acid, palmitic acid, stearic acid,
oleic acid, linoleic acid, linolenic acid, eicosadienoic acid,
arachidonic acid, behenic acid, erucic acid, ricinoleic acid,
12-hydroxystearic acid, and hydrogenated castor oil fatty acids.
These are used singly or as a mixture.
[0096] Polyglycerol condensed hydroxy fatty acid ester is prepared
by a reaction of polyglycerol and condensed hydroxy fatty acid.
Examples of the constituent of the polyglycerol condensed hydroxy
fatty acid ester, i.e., polyglycerol include those exemplified as
the constituent of the polyglycerol fatty acid ester.
[0097] The condensed hydroxy fatty acid as the other constituent of
the polyglycerol condensed hydroxy fatty acid ester is a condensed
product of a hydroxy fatty acid. Any hydroxy fatty acid having one
or more hydroxyl groups in the molecule can be used, and examples
thereof include ricinoleic acid, 12-hydroxystearic acid, and
hydrogenated castor oil fatty acids. The degree of condensation of
condensed hydroxy acid is, for example, not less than 3, preferably
3 to 8. The condensed hydroxy fatty acids are used singly or as a
mixture.
[0098] Commercially available products can be used as the
polyglycerol fatty acid ester and the polyglycerol condensed
hydroxy fatty acid ester. Examples of commercially available
products of the polyglycerol fatty acid ester include Chirabasol
series such as trade names "Chirabasol VR-10" and "Chirabasol VR-2"
made by Taiyo Kagaku Co., Ltd.
[0099] In the present invention, the polylactic acid film or sheet
contains the core-shell-structured polymer (b) composed of a
particulate rubber and a graft layer formed on the outside of the
rubber as the reforming agent (E) such that the weight ratio of the
polylactic acid (A) to the core-shell-structured polymer (b)
composed of a particulate rubber and a graft layer formed on the
outside of the rubber is preferably 99:1 to 80:20 ((A):(b)), more
preferably 97:3 to 90:10 ((A):(b)). The core-shell-structured
polymers (b) composed of a particulate rubber and a graft layer
formed on the outside of the rubber may be used singly or in
combinations of two or more.
[0100] An excessively small amount of the core-shell-structured
polymer (b) composed of a particulate rubber and a graft layer
formed on the outside of the rubber leads to an insufficient effect
of reforming physical properties. An excessively large amount of
the core-shell-structured polymer (b) composed of a particulate
rubber and a graft layer formed on the outside of the rubber
readily reduces the degree of crystallization and the rate of
crystallization, and may cause the core-shell-structured polymer
(b) composed of a particulate rubber and a graft layer formed on
the outside of the rubber to bleed out. When the polylactic acid
film or sheet containing the core-shell-structured polymer (b)
composed of a particulate rubber and a graft layer formed on the
outside of the rubber in the above range is used as the substrate
for the separator, tear resistance can be improved without reducing
heat resistance.
[0101] Examples of the particulate rubber that forms the core in
the core-shell-structured polymer (b) composed of a particulate
rubber and a graft layer formed on the outside of the rubber
include acrylic rubbers, butadiene rubbers, and silicone-acrylic
composite rubbers. Examples of a polymer that forms the shell
include styrene resins such as polystyrene, and acrylic resins such
as polymethyl methacrylate.
[0102] The average particle size of the core-shell-structured
polymer (a set of primary particles) is, for example, 50 to 500
.mu.m, preferably 100 to 250 .mu.m. When this polymer is compounded
with the polylactic acid (A) and is melt kneaded, its primary
particles are dispersed. The primary particles have an average
particle size of 0.1 to 0.6 .mu.m, for example.
[0103] Commercially available products can be used as the
core-shell-structured polymer. Examples of commercially available
products of the core-shell-structured polymer include PARALOID
series (particularly, PARALOID EXL series) such as trade name
"PARALOID EXL2315" made by Rohm and Haas Japan K.K., and METABLEN S
type such as trade name "METABLEN S-2001," METABLEN W type such as
trade name "METABLEN W-450A," METABLEN C type such as trade name
"METABLEN C-223A," and METABLEN E type such as trade name "METABLEN
E-901" made by MITSUBISHI RAYON CO., LTD.
[0104] In the present invention, the polylactic acid film or sheet
contains the soft aliphatic polyester (c) as the reforming agent
(E) such that the weight ratio of the polylactic acid (A) to the
soft aliphatic polyester (c) is preferably 95:5 to 60:40 ((A):(c)),
more preferably 90:10 to 80:20 ((A):(c)). The soft aliphatic
polyesters (c) may be used singly or in combinations of two or
more.
[0105] An excessively small amount of the soft aliphatic polyester
(c) leads to an insufficient effect of reforming physical
properties. An excessively large amount of the soft aliphatic
polyester (c) readily reduces the degree of crystallization and the
rate of crystallization, and may cause the soft aliphatic polyester
(c) to bleed out. When the polylactic acid film or sheet containing
the soft aliphatic polyester (c) in the above range is used as the
separator substrate for the separator, tear resistance can be
improved without reducing heat resistance.
[0106] The soft aliphatic polyester (c) includes aliphatic
polyesters and aliphatic and aromatic copolymerization polyesters.
The soft aliphatic polyester (c) (aliphatic polyesters and
aliphatic and aromatic copolymerization polyesters) is prepared
from a polyhydric alcohol such as diol and a polyvalent carboxylic
acid such as dicarboxylic acid, and examples thereof include
polyesters comprising at least an aliphatic diol as diol and at
least an aliphatic dicarboxylic acid as dicarboxylic acid; and
polymers of aliphatic hydroxycarboxylic acids having not less than
4 carbon atoms. Examples of the aliphatic diol include aliphatic
diols having 2 to 12 carbon atoms (including alicyclic diols) such
as ethylene glycol, 1,2-propanediol, 1,3-propanediol,
2,2-dimethyl-1,3-propanediol, 1,2-butanediol, 1,4-butanediol,
neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, cyclohexanediol,
1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol. Examples
of the aliphatic dicarboxylic acid include saturated aliphatic
dicarboxylic acid having 2 to 12 carbon atoms (including alicyclic
dicarboxylic acids) such as succinic acid, malonic acid, glutaric
acid, adipic acid, pimelic acid, suberic acid, azelaic acid,
sebacic acid, dodecanedioic acid, 1,3-cyclohexanedicarboxylic acid,
and 1,4-cyclohexanedicarboxylic acid. In the polyesters comprising
at least an aliphatic diol as the diol component and at least an
aliphatic dicarboxylic acid as the dicarboxylic acid component, the
proportion of the aliphatic diol to the entire diol component is,
for example, not less than 80% by weight, preferably not less than
90% by weight, more preferably not less than 95% by weight. Besides
the aliphatic diol, aromatic diol or the like may be contained. In
the polyesters comprising at least an aliphatic diol as the diol
component and at least an aliphatic dicarboxylic acid as the
dicarboxylic acid component, the proportion of the aliphatic
dicarboxylic acid to the entire dicarboxylic acid component is for
example, not less than 20% by weight, preferably not less than 30%
by weight, more preferably not less than 50% by weight. Besides the
aliphatic dicarboxylic acid, aromatic dicarboxylic acid (such as
terephthalic acid) may be contained. Examples of the aliphatic
hydroxycarboxylic acid having not less than 4 carbon atoms include
hydroxycarboxylic acids having 4 to 12 carbon atoms such as
hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid,
hydroxyhexanoic acid, hydroxydecanoic acid, and hydroxydodecanoic
acid. The soft aliphatic polyester (c) (aliphatic polyesters and
aliphatic and aromatic copolymerization polyesters) has a weight
average molecular weight of, for example, 50000 to 400000,
preferably 80000 to 250000.
[0107] Typical examples of the soft aliphatic polyester (c) include
polybutylene succinate, polybutylene succinate adipate,
polyethylene succinate, polyethylene succinate adipate,
polybutylene adipate terephthalate, polybutylene sebacate
terephthalate, and polyhydroxylalkanoate.
[0108] Commercially available products can be used as the soft
aliphatic polyester (c). Examples of polybutylene succinate include
trade name "GS Pla AZ91T" made by Mitsubishi Chemical Corporation,
examples of polybutylene succinate adipate include trade name "GS
Pla AD92W" made by Mitsubishi Chemical Corporation, and examples of
polybutylene adipate terephthalate include trade name "Ecoflex"
made by BASF Japan Ltd.
[0109] In the present invention, the polylactic acid film or sheet
may optionally contain a variety of additives in the range not to
impair the effects of the present invention. Examples of such
additives include antioxidants, ultraviolet absorbing agents,
plasticizers, stabilizers, mold release agents, antistatic agents,
colorants (such as white pigments), drip preventing agents, flame
retardants, hydrolysis preventing agents, foaming agents, and
fillers.
[0110] In the present invention, the polylactic acid film or sheet,
which has high degree of crystallization, also has high solvent
resistance. For example, the polylactic acid film or sheet has a
degree of swelling of for example, not more than 2.5, preferably
not more than 2.0 to any solvent of ethyl acetate and toluene. The
degree of swelling can be determined as follows: A film or sheet
sample (50 mm.times.50 mm.times.thickness of 0.05 mm) is immersed
in a solvent for 15 minutes, and is taken out from the solvent;
then, the solvent on the surface of the sample is removed with a
waste cloth, and the weight of the sample after immersion is
divided by that before immersion.
[0111] In the present invention, the polylactic acid film or sheet
can also maintain high mechanical properties such as rigidity and
high elasticity. For example, the polylactic acid film or sheet in
the present invention has an initial elastic modulus of usually not
less than 1000 MPa, preferably not less than 1500 MPa in the flow
direction (MD). The upper limit of the initial elastic modulus is
typically approximately 3500 MPa (for example, approximately 3000
MPa) in the flow direction (MD). The polylactic acid film or sheet
in the present invention has a breaking strength of usually not
less than 30 MPa, preferably not less than 35 MPa in the flow
direction (MD). The upper limit of the breaking strength is
typically approximately 150 MPa (for example, approximately 120
MPa).
[0112] The polylactic acid film or sheet in the present invention
has an elongation of usually not less than 2.5%, preferably not
less than 3.5% in the flow direction (MD). The upper limit of the
elongation is typically approximately 15% (for example,
approximately 12%) in the flow direction (MD). When the soft
aliphatic polyester (c) is used as the reforming agent (E), the
polylactic acid film or sheet has an elongation of usually not less
than 5%, preferably not less than 10%, more preferably not less
than 20% in the flow direction (MD). The upper limit of the
elongation is typically 150%, preferably 120%, more preferably 100%
in the flow direction (MD).
[0113] The initial elastic modulus, the breaking strength, and the
elongation were determined with a tensile tester according to JIS K
7161: Plastics--Determination of tensile properties.
[0114] apparatus: tensile tester (Autograph AG-20kNG, manufactured
by SHIMADZU Corporation)
[0115] sample size: thickness of 0.05 mm.times.width of 10
mm.times.length of 100 mm (a sample was cut out such that the
direction of the sample parallel to the length direction of the
film or sheet corresponded to the flow direction (MD) in film
formation)
[0116] measurement condition:
[0117] distance between chucks: 50 mm
[0118] tensile rate: 300 mm/min
[0119] In the present invention, the polylactic acid film or sheet
can have any thickness, which is usually 10 to 500 .mu.m,
preferably 20 to 400 .mu.m, more preferably 30 to 300 .mu.m.
[Method of Producing Separator]
[0120] The method of producing a separator in the present invention
is
[0121] a method of producing a separator including a separator
substrate composed of a polylactic acid film or sheet prepared by
forming a resin composition comprising polylactic acid (A) into a
film by a melt film forming method, the method comprising:
[0122] a melt film forming step of melt forming the resin
composition,
[0123] a cooling solidifying step of cooling and solidifying the
resin composition after the melt film forming step to prepare a
film or sheet, and
[0124] a crystallization promoting step of heating the film or
sheet after the cooling solidifying step to promote crystallization
of the film or sheet,
[0125] wherein a resin temperature in the melt film forming step is
within the range of (Tm)-15.degree. C. to (Tm)+15.degree. C. where
Tm represents a melting temperature of the resin composition during
raising of temperature, and
[0126] in at least part of the crystallization promoting step,
crystallization of the film or sheet is promoted within the
temperature range of (Tc)+10.degree. C. to (Tc)+50.degree. C. where
Tc represents a crystallization temperature of the resin
composition during the raising of temperature.
[0127] For example, the polylactic acid film or sheet can be
produced with a continuous melt kneader with a twin screw extruder
or the like, or a batch type melt kneader such as a pressure
kneader, a Banbury mixer, a roll kneader by uniformly dispersing
the components to prepare a resin composition containing the
polylactic acid (A), forming the resin composition into a film by
extrusion such as a T die method and an inflation method,
calendering, or polishing, and cooling and solidifying the film.
The melt film forming method is a method in which preferably a melt
resin composition is passed through between two metal rolls to be
formed into a film of a desired thickness. The method is more
preferably calendering or polishing, particularly preferably
calendering.
[0128] The resin temperature in the melt film forming step is
within the range of (Tm)-15.degree. C. to (Tm)+15.degree. C.,
preferably (Tm)-15.degree. C. to (Tm)+5.degree. C., more preferably
(Tm)-10.degree. C. to (Tm), particularly preferably (Tm)-5.degree.
C. to (Tm) where Tm represents a melting temperature of the resin
composition during raising of temperature.
[0129] In particular, when the resin composition does not contain
the reforming agent (E), the resin temperature is within the range
of preferably (Tm)-15.degree. C. to (Tm)+5.degree. C., more
preferably (Tm)-10.degree. C. to (Tm) where Tm represents a melting
temperature of the resin composition during raising of
temperature.
[0130] In particular, when the resin composition further contains
the reforming agent (E), the resin temperature is within the range
of preferably (Tm)-10.degree. C. to (Tm)+5.degree. C., more
preferably (Tm)-5.degree. C. to (Tm) where Tm represents a melting
temperature of the resin composition during raising of
temperature.
[0131] The resin temperature set within such a range attains an
effect of suppressing oriented crystallization during film
formation.
[0132] In particular, from the viewpoint of consistent control to
be a predetermined temperature, it is desired that in the melt film
forming step, the resin composition be contacted with a metal roll
having a predetermined surface temperature. Accordingly, also in
the step, the resin composition containing the polylactic acid (A)
is desirably formed of a composition readily peelable from the
metal roll. From the viewpoint, addition of the acidic functional
group-modified olefin polymer (B) is preferable.
[0133] The method of producing a separator in the present invention
preferably comprises a residual stress relaxing step after the melt
film forming step and before the cooling solidifying step, the step
of keeping the resin composition within a predetermined temperature
range to relax the residual stress of the resin composition. The
predetermined temperature (residual stress relaxing temperature)
can be any temperature, for example, within the temperature range
of (Tm)-70.degree. C. to (Tm)-20.degree. C., preferably
(Tm)-60.degree. C. to (Tm)-20.degree. C., more preferably
(Tm)-60.degree. C. to (Tm)-23.degree. C., still more preferably
(Tm)-50.degree. C. to (Tm)-25.degree. C., particularly preferably
(Tm)-50.degree. C. to (Tm)-30.degree. C.
[0134] In particular, when the resin composition does not contain
the reforming agent (E), the residual stress relaxing temperature
is within the temperature range of preferably (Tm)-60.degree. C. to
(Tm)-23.degree. C., more preferably (Tm)-50.degree. C. to
(Tm)-30.degree. C.
[0135] In particular, when the resin composition further contains
the reforming agent (E), the residual stress relaxing temperature
is within the temperature range of preferably (Tm)-60.degree. C. to
(Tm)-20.degree. C., more preferably (Tm)-60.degree. C. to
(Tm)-23.degree. C., still more preferably (Tm)-50.degree. C. to
(Tm)-25.degree. C., particularly preferably (Tm)-50.degree. C. to
(Tm)-30.degree. C. The preferred temperature range may depend on
types of the reforming agent (E) or the like.
[0136] The residual stress relaxing temperature set within such a
range further enhances the effect of relaxing the residual stress
and further reduces the risk of extremely thermally shrinking the
prepared film or sheet during usage. This setting of the residual
stress relaxing temperature enables the resultant crystallized film
or sheet to keep the shape up to a temperature close to the melting
point of polylactic acid. Such a film or sheet can be sufficiently
used in applications requiring heat resistance, in which the film
or sheet have not been able to be used. The residual stress
relaxing step can use any specific method of keeping the resin
composition at a predetermined temperature. Examples thereof
include a method of contacting a film sample with a take-off roll
kept at a predetermined temperature.
[0137] In at least part of the crystallization promoting step,
crystallization of the film or sheet is promoted within the
temperature range of (Tc)+10.degree. C. to (Tc)+50.degree. C. where
Tc represents a crystallization temperature of the resin
composition during the raising of temperature. Crystallization of
the film or sheet is promoted within the temperature range of
preferably (Tc)+20.degree. C. to (Tc)+45.degree. C., more
preferably (Tc)+20.degree. C. to (Tc)+40.degree. C. where Tc
represents a crystallization temperature of the resin composition
during the raising of temperature. The crystallization temperature
set within such a temperature range further improves the effect of
promoting crystallization to improve a production rate.
[0138] In particular, from the viewpoint of consistent control to
be a predetermined temperature, it is desired that in the
crystallization promoting step, the film or sheet be contacted with
a metal roll having a predetermined surface temperature.
Accordingly, also in the step, the film or sheet is desirably
formed of a composition readily peelable from the metal roll. From
the viewpoint, addition of the acidic functional group-modified
olefin polymer (B) is preferable.
[0139] The time for the crystallization promoting step is
preferably as long as possible. The time depends on the degree of
crystallization of the resin composition as a conclusion and cannot
be specified in general. The time is usually 10 to 120 seconds,
preferably 20 to 90 seconds, more preferably 30 to 60 seconds.
[0140] In the crystallization promoting step, an optimal
temperature condition for the crystallization promoting step can
always be obtained, even if the crystallization temperature (Tc)
changes due to addition of an additional nucleator or the like
during lowering of temperature of the resin composition, by
determining the temperature at the highest exothermic peak
accompanied by crystallization during lowering of temperature in
advance in the measurement with a differential scanning calorimeter
(DSC). At this time, it is barely necessary to consider changes in
the shape of the film or sheet prepared which are caused by heating
at the temperature. Preferably, the temperature attains a film or
sheet having a thermal deformation rate of not more than 40%.
[0141] Before and/or after the crystallization promoting step,
monoaxial or twin-axial drawing (preferably twin-axial drawing) may
be performed. The drawing may further increase crystallization. The
drawing temperature is, for example, 60 to 100.degree. C.
[0142] In the method of producing a polylactic acid film or sheet
comprising the crystallization promoting step, the steps from the
melt film forming step to the cooling solidifying step are
continuously performed. This continuous mode is preferable for a
reduction in the process time, and thus productivity. More
preferably, the crystallization step is provided continuously
subsequent to the cooling solidifying step (for example, the film
or sheet is passed through a heat roll). Examples of such a method
include methods using a calendering film forming machine, a
polishing film forming machine, or the like.
[Calendering Film Formation]
[0143] A schematic view of an example of a calendering film forming
machine used in the production method will be shown in FIG. 1.
Hereinafter, FIG. 1 will be described in detail.
[0144] While a first roll 1, a second roll 2, a third roll 3, and a
fourth roll 4 are being controlled, a melt resin composition is
rolled between these four calender rolls to be gradually thinned,
and is controlled to have a desired thickness finally when the
resin composition is passed through between the third roll 3 and
the fourth roll 4. In the calendering film formation, film
formation of the resin composition from the first roll 1 to the
fourth roll 4 corresponds to the "melt film forming step." A
take-off roll 5 represents a group of rolls contacted by a resin
composition 8 formed into a film by melt film forming first. The
take-off roll 5 includes one or two or more (three in FIG. 1)
rolls, which peel off the melt resin composition 8 from the fourth
roll 4. When the take-off roll 5 includes a plurality of rolls as
above and the temperatures of the respective rolls can be
controlled, the temperatures of the respective rolls are preferably
the same. The temperatures may be different if the temperatures
fall within a desired temperature range.
[0145] The take-off roll 5 contacts with the film sample to relax
the residual stress (residual stress relaxing step). At this time,
the (three in FIG. 1) take-off rolls often have approximately the
same surface temperature, which is the stress relaxing temperature
(.degree. C.). The three take-off rolls may have different
temperatures. In this case, preferably, the temperatures of these
take-off rolls are within the temperature range above.
[0146] Two cooling rolls 6 and 7 cool the resin composition 8 when
the resin composition 8 is passed through between these rolls,
thereby to solidify the resin composition 8 and mold the surface
into a desired shape (cooling solidifying step). For this reason,
typically, one roll (for example, cooling roll 6) is a metal roll
having a designed surface to produce the shape of the surface of
the resin composition 8, and the other roll (for example, cooling
roll 7) is a rubber roll. Arrows in the drawing represent
rotational directions of the respective rolls. A bank 9 (resin
pool) is shown.
[0147] Subsequently, the cooled and solidified film is heated with
a heat roll not shown in FIG. 1 controlled to be any temperature to
promote crystallization (crystallization promoting step).
[Polishing Film Formation]
[0148] A schematic view of an example of a polishing film forming
machine used in the production method will be shown in FIG. 2.
Hereinafter, FIG. 2 will be described in detail.
[0149] A tip 10 of an extruder (not shown) is disposed between a
second roll 2 and a third roll 3 heated, and a melt resin
composition 8 is continuously extruded between the second roll 2
and the third roll 3 at a preset extrusion rate. The extruded resin
composition 8 is rolled between the second roll 2 and the third
roll 3 to be thinned, and is controlled to have a desired thickness
finally when the resin composition 8 is passed through between the
third roll 3 and the fourth roll 4. In polishing film formation,
the film formation of the resin composition 8 from the second roll
2 to the fourth roll 4 corresponds to the "melt film forming step."
Subsequently, the resin composition 8 is passed through one or two
or more (three in FIG. 2) take-off rolls 5 (residual stress
relaxing step), and finally passed through the cooling roll
(cooling rolls 6 and 7 in FIG. 2) (cooling solidifying step) to
prepare a solidified film or sheet.
[0150] Subsequently, the cooled and solidified and formed film is
heated with a heat roll not shown in FIG. 2 controlled to be any
temperature to promote crystallization (crystallization promoting
step).
[0151] In the present invention, to enhance the adhesion to an
adjacent layer, the surface of the separator substrate may be
optionally subjected to a standard surface treatment, for example,
an oxidation treatment by a chemical or physical method, such as
chromic acid treatment, exposure to ozone, exposure to flame,
exposure to high voltage electric shock, and ionization radiation
treatment.
[Release Agent-Treated Layer]
[0152] The separator according to the present invention includes a
release agent-treated layer on at least one surface of the
separator substrate.
[0153] Any release agent (mold release agent) used for forming a
release agent-treated layer can be used, for example, silicone
release agents, fluorine release agents, long-chain alkyl release
agents, and polyolefin release agents. These release agents may be
used singly or in combinations of two or more.
[0154] Any release agent can be used as long as the release agent
can be formed on the separator substrate in the form of a coating
film demonstrating moderate release properties for applications and
not adversely affecting the pressure-sensitive adhesive. For
example, from the viewpoint of demonstration of high release
properties to the adherent surface of a pressure-sensitive adhesive
tape or sheet or the like, release agents enabling formation of a
coating film having a peel force to the adherent surface of
approximately 0 to 25 N/50 mm (preferably approximately 0.1 to 10
N/50 mm) are preferable.
[0155] Among these, silicone release agents are preferable from the
viewpoint of release performance. Any silicone release agent can be
used, and typical examples thereof include thermosetting addition
silicone release agents (thermosetting addition polysiloxane
release agents).
[0156] The thermosetting addition silicone release agent contains
polyorganosiloxane containing an alkenyl group as a functional
group in the molecule (alkenyl group-containing silicone) and
polyorganosiloxane containing a hydrosilyl group as a functional
group in the molecule as essential constituents.
[0157] Preferable polyorganosiloxane containing an alkenyl group as
a functional group in the molecule is especially polyorganosiloxane
having two or more alkenyl groups in the molecule. Examples of the
alkenyl group include a vinyl group (ethenyl group), an allyl group
(2-propenyl group), a butenyl group, a pentenyl group, and hexenyl
group. The alkenyl group typically bonds to a silicon atom of the
polyorganosiloxane forming the main chain or the skeleton (such as
a silicon atom at a terminal and a silicon atom in the main
chain).
[0158] Examples of the polyorganosiloxane forming the main chain or
the skeleton include polyalkylalkylsiloxanes (polydialkylsiloxanes)
such as polydimethylsiloxane, polydiethylsiloxane, and
polymethylethylsiloxane; polyalkylarylsiloxane; and copolymers
comprising several silicon atom-containing monomer components [such
as poly(dimethylsiloxane-diethylsiloxane)]. Among these,
polydimethylsiloxane is suitable. That is, preferable examples of
the polyorganosiloxane containing an alkenyl group as a functional
group in the molecule specifically include polydimethylsiloxanes
having a vinyl group, a hexenyl group, or the like as a functional
group.
[0159] The polyorganosiloxane crosslinking agent containing a
hydrosilyl group as a functional group in the molecule is
polyorganosiloxane having a hydrogen atom bonding to the silicon
atom (particularly, silicon atom having Si--H bond) in the
molecule, and is particularly preferably polyorganosiloxane having
two or more silicon atoms having Si--H bond in the molecule. The
silicon atom having Si--H bond may be a silicon atom in the main
chain or a silicon atom in the side chain. Namely, the silicon atom
having Si--H bond may be contained as a constitutional unit of the
main chain or as a constitutional unit of the side chain. The Si--H
bond can have any number of silicon atoms of two or more. The
polyorganosiloxane crosslinking agent containing a hydrosilyl group
as a functional group in the molecule is specifically suitably
polymethylhydrogensiloxane,
poly(dimethylsiloxane-methylhydrogensiloxane), and the like.
[0160] The release agent according to the present invention may
contain a reaction inhibitor to give storage stability at room
temperature. For example, when the thermosetting addition silicone
release agent is used as the release agent, specific examples of
the reaction inhibitor include 3,5-dimethyl-1-hexyn-3-ol,
3-methyl-1-penten-3-ol, 3-methyl-3-penten-1-yne, and
3,5-dimethyl-3-hexen-1-yne.
[0161] The release agent may optionally contain a release control
agent in addition to the components above. For example, when the
thermosetting addition silicone release agent is used as the
release agent, specifically, a release control agent such as an MQ
resin, or polyorganosiloxane having no alkenyl group or hydrosilyl
group (such as polydimethylsiloxane having an end capped by a
trimethylsiloxy group) may be added. These components can be added
in any content in the thermosetting addition silicone release
agent. The content thereof is preferably 1 to 30% by weight.
[0162] The release agent may optionally contain a variety of
additives. Examples of the optional additives include fillers,
antistatic agents, antioxidants, ultraviolet absorbing agents,
plasticizers, and colorants (such as dyes and pigments).
[0163] The release agent-treated layer can be formed by a known
standard method. Examples thereof include a method of applying a
release agent composition containing the release agent onto the
separator substrate (intermediate layer when the intermediate layer
is disposed on the separator substrate). Application can be
performed with a coater, an extruder, a printer, or the like
typically used in formation of the release agent-treated layer.
[0164] The release agent-treated layer can have any thickness
according to its applications or the like, which is, for example,
0.02 to 1 .mu.m, preferably 0.05 to 0.7 .mu.m, more preferably
approximately 0.1 to 0.5 .mu.m.
[0165] The separator according to the present invention may
optionally have an additional layer (intermediate layer) between
the separator substrate and the release agent-treated layer.
EXAMPLES
[0166] Hereinafter, the present invention will be more specifically
described using Examples and Comparative Examples. The present
invention will not be limited to these. Evaluations in Examples and
the like were made as follows.
[0167] The following materials were used in Examples and the
like.
<Polylactic Acid (A)>
[0168] A1: trade name "Terramac TP-4000" (made by Unitika
Limited)
<Acidic Functional Group-Modified Olefin Polymer (B)>
[0169] B1: maleic anhydride group-containing modified polypropylene
(weight average molecular weight: 32000, acid value: 52 mgKOH/g,
trade name "Umex 1010," made by Sanyo Chemical Industries,
Ltd.)
<Fluorine-Containing Polymer (C)>
[0170] C1: acrylic-modified polytetrafluoroethylene (trade name
"METABLEN A-3000," made by MITSUBISHI RAYON CO., LTD.)
<Crystallization Promoter (D)>
[0171] D1: zinc phenyl phosphonate (trade name "ECOPROMOTE," made
by Nissan Chemical Industries, Ltd.)
<Reforming Agent (E)>
[0172] E(a): polyglycerol fatty acid ester (number average
molecular weight Mn: 1300, trade name "Chirabasol VR-17," made by
Taiyo Kagaku Co., Ltd.)
[0173] E(b): core-shell-structured polymer (acrylic
rubber/polymethyl methacrylate-styrene core-shell-structured
polymer, trade name "PARALOID EXL2315," made by The Dow Chemical
Company)
[0174] E(c): soft aliphatic polyester (polybutylene adipate
terephthalate (trade name "Ecoflex," made by BASF Japan Ltd.)
Examples 1 to 7
[0175] Each of resin compositions was prepared in the compounding
proportion shown in Table 1 below, and was melt kneaded with a
Banbury mixer. By calendering with a calender with four reverse-L
shaped rolls, the resin composition was formed into a film to have
a thickness of 50 .mu.m (melt film forming step). Next, as shown in
FIG. 1, three rolls (take-off roll) heatable to any temperature
were disposed immediately after the melt film forming step. The
melt film formed resin composition was passed through the three
rolls in a staggered manner, and then through cooling rolls to
solidify the resin composition. A film was prepared. Subsequently,
as shown in Table 1 below, the cooled and solidified and formed
film was heated with a heat roll controlled to be any temperature,
thereby to promote crystallization (crystallization promoting
step).
[0176] The temperature of the resin composition in the melt film
forming step ("resin temperature in the melt film forming step")
was the surface temperature of a roll corresponding to the fourth
roll 4 in FIG. 1. The temperature of the resin composition in the
crystallization promoting step ("crystallization promoting
temperature") was the surface temperature of the heat roll. The
film forming rate was 5 m/min.
Comparative Examples 1 to 9
[0177] Each of resin compositions was prepared in the compounding
proportion shown in Table 2 below in the same manner as in Examples
except that the crystallization promoting step was not performed,
and was formed into a film by calendering under film forming
conditions shown in Table 2 below.
[0178] The physical properties of the substrate were determined as
follows.
<Melting Temperature (.degree. C.)>
[0179] A temperature at the highest endothermic peak accompanied by
melting of the resin composition after film formation during
re-raising of temperature was measured with a DSC (differential
scanning calorimeter). The temperature was defined as a melting
temperature (Tm; also referred to as a crystal melting peak
temperature).
<Crystallization Temperature (.degree. C.)>
[0180] A temperature at the highest exothermic peak accompanied by
crystallization of the resin composition after film formation
during the raising of temperature from room temperature was
measured with a DSC. The temperature was defined as a
crystallization temperature (Tc; crystallization temperature during
the raising of temperature, also referred to as a crystallization
peak temperature).
<Resin Temperature (.degree. C.) in Melt Film Forming
Step>
[0181] As above, in Examples and Comparative Examples, the surface
temperature of the fourth roll was measured, and was defined as the
"resin temperature in the melt film forming step" (resin
temperature in the melt film forming step).
<Residual Stress Relaxing Temperature (.degree. C.)>
[0182] In this embodiment, a film sample was contacted with a
take-off roll to relax residual stress. At this time, surface
temperatures of three take-off rolls in FIG. 1 (take-off roll
temperatures) were approximately the same, and the temperatures
were defined as a stress relaxing temperature (.degree. C.). The
temperatures of the three take-off rolls may be different if the
temperatures fall within the temperature range.
<Crystallization Promoting Temperature (.degree. C.)>
[0183] In this embodiment, the formed film was heated with a heat
roll controlled to be any temperature, thereby to promote
crystallization. The temperature of the heat roll was defined as a
crystallization promoting temperature.
<Results of Film Forming Properties>
[0184] (1) Plate out to roll: dirt on the surface of the roll was
visually evaluated, and was considered ".largecircle." (absent) if
the surface of the roll had no dirt and "x" (present) if the
surface of the roll had dirt. (2) Peelability: peelability of the
melt film formed resin composition from the fourth roll 4 in FIG. 1
was evaluated, and was considered ".largecircle." (good) if the
resin composition could be taken with the take-off roll 5, and "x"
(poor) if the resin composition could not be taken with the
take-off roll 5. (3) State of film surface: the surface of the
prepared film was visually observed, and was considered
".largecircle." (good) if the film surface was smooth without
roughness, and "x" (poor) if the surface of the film had bank marks
(depressions and projections caused by uneven flow of the resin),
roughness, or pin holes.
<Tear Strength (N/mm)>
[0185] Tear strength was measured according to JIS K7128-3:
Plastics--Film and Sheeting--Determination of Tear Resistance, Part
3: Right angled tear method. The following apparatus and conditions
were used in the measurement.
[0186] apparatus: tensile tester (Autograph AG-20kNG, manufactured
by SHIMADZU Corporation)
[0187] sample size: shape of the test piece according to JIS
[0188] condition: tensile rate: 200 mm/min
[0189] The sample used for the evaluation was cut out such that the
tear direction of the sample corresponded to the flow direction
(hereinafter referred to as MD) in film formation.
[0190] Method of calculating tear strength: Expression (3) below
was used.
T=(F/d) (3)
[0191] T: tear strength (N/mm)
[0192] F: the largest tensile load (N)
[0193] d: thickness of the test piece (mm)
<Amount of Crystallization Heat .DELTA.Hc' (J/g) after Film
Formation>
[0194] The amount of heat .DELTA.Hc (J/g) at the exothermic peak
accompanied by crystallization of the film sample after film
formation during the raising of temperature, and the amount of heat
.DELTA.Hm (J/g) accompanied by melting when the temperature was
raised to 200.degree. C., was lowered to 0.degree. C., and was then
raised again were measured with a DSC. From the .DELTA.Hc (J/g) and
the .DELTA.Hm (J/g), .DELTA.Hc' was calculated using Expression (5)
below where .DELTA.Hc' was the amount of crystallization heat after
film formation (amount of melt endotherm in crystallized portions
during film formation).
.DELTA.Hc'=.DELTA.Hm-.DELTA.Hc (5)
[0195] The following DSC was used in the measurements of the
crystallization temperature, the melting temperature, a relative
crystallization rate, and the amount of crystallization heat
.DELTA.Hc' after film formation:
[0196] apparatus: DSC6220 manufactured by SII NanoTechnology
Inc.
[0197] The measurement conditions are:
[0198] range of temperature in the measurement: 20.degree. C. to
200.degree. C. to 0.degree. C. to 200.degree. C. (namely, first,
the measurement during the raising of temperature from 20.degree.
C. to 200.degree. C., followed by the measurement during lowering
of temperature from 200.degree. C. to 0.degree. C., finally
followed by the measurement during re-raising of temperature from
0.degree. C. to 200.degree. C.)
[0199] temperature raising/falling rate: 2.degree. C./min
[0200] atmosphere for the measurement: under a nitrogen atmosphere
(200 ml/min)
[0201] No exothermic peak accompanied by crystallization was found
during the re-raising of temperature. From this, it was determined
that 100% of crystallizable regions was crystallized at the
temperature falling rate of 2.degree. C./min, and adequacy of the
calculation expression for the amount of crystallization heat after
film formation was confirmed.
<Rate of Dimensional Change Due to Heating>
[0202] A film measuring 100 mm.times.100 mm was cut out, was marked
with a gauge line at 50 mm in the flow direction (hereinafter
referred to as MD) and the transverse direction (hereinafter
referred to as TD) during film formation. The film was placed in an
oven heated to 120.degree. C. for 1 minute, and was examined for
the dimensional change after the film was extracted.
[0203] Method of calculating a rate of dimensional change due to
heating; the gauge length L1 before a test and the gauge length L2
after the test were measured, and the rate of dimensional change
due to heating was calculated from Expression (1):
rate of dimensional change due to heating (%)=(L2-L1)/L1.times.100
(1)
(Evaluation) The dimensional change rates by heating of not more
than .+-.3% in MD and TD are accepted.
<Rate of Dimensional Change Due to Loaded Heating>
[0204] A film measuring 100 mm (MD).times.20 mm (TD) was cut out,
and was marked with a gauge line at 50 mm in MD. While a load of
300 g/mm.sup.2 was being applied in MD, the film was placed in an
oven heated to 100.degree. C. for 1 minute. The dimensional change
in MD of the film was examined after the film was extracted.
[0205] Method of calculating a rate of dimensional change due to
loaded heating; the gauge length L3 before a test and the gauge
length L4 after the test were measured, and the rate of dimensional
change due to loaded heating was calculated from Expression
(2):
rate of dimensional change due to heating (%)=(L4-L3)/L3.times.100
(2)
(Evaluation) The rate of dimensional change due to loaded heating
of not more than .+-.3% is accepted.
[0206] This evaluation was performed as an alternative evaluation
in consideration of a drying step during actual application of the
pressure-sensitive adhesive on the premise that the film was wound
into a roll while a certain tension was being applied to the
film.
[0207] Results of evaluation in Examples 1 to 7 and Comparative
Examples 1 to 9 are shown in Tables 1 and 2 below. In Example 1 and
Comparative Examples 1 to 3 where the reforming agent is not added,
Example 1 showed high tear resistance and high heat resistance. In
contrast, Comparative Example 1, which includes no crystallization
step, shows high tear resistance. Unfortunately, the film in
Comparative Example 1 cannot endure heat load deformation due to
its low amount of crystallization heat. Comparative Example 2 shows
poor tear resistance although high heat resistance is attained by
crystallization during film formation. Comparative Example 3 shows
poor tear resistance and poor heat resistance because the residual
stress is not relaxed due to a low temperature of the take-off
roll.
[0208] In Examples 2 and 3 and Comparative Examples 4 and 5 where
the reforming agent E(a) is added, Examples 2 and 3 showed high
tear resistance and high heat resistance. Examples 2 and 3 have
tear strength greater than that in Example 1 where the reforming
agent is not added, and show the effect of compounding the
reforming agent. In contrast, Comparative Example 4, which includes
no crystallization step, shows high tear resistance. Unfortunately,
the film in Comparative Example 4 cannot endure heat load
deformation due to its low amount of crystallization heat.
Comparative Example 3 shows poor tear resistance although high heat
resistance is attained by crystallization during film
formation.
[0209] In Examples 4 and 5 and Comparative Examples 6 and 7 where
the reforming agent E(b) is added, Examples 4 and 5 showed high
tear resistance and high heat resistance. Examples 4 and 5 have
tear strength greater than that in Example 1 where the reforming
agent is not added, and show the effect of compounding the
reforming agent. In contrast, Comparative Example 6, which includes
no crystallization step, shows high tear resistance. Unfortunately,
the film in Comparative Example 6 cannot endure heat load
deformation due to its low amount of crystallization heat.
Comparative Example 5 shows poor tear resistance although high heat
resistance is attained by crystallization during film
formation.
[0210] In Examples 6 and 7 and Comparative Examples 8 and 9 where
the reforming agent E(c) is added, Examples 6 and 7 showed high
tear resistance and high heat resistance. Examples 6 and 7 have
tear strength greater than that in Example 1 where the reforming
agent is not added, and show the effect of compounding the
reforming agent. In contrast, Comparative Example 8, which includes
no crystallization step, shows high tear resistance. Unfortunately,
the film in Comparative Example 8 cannot endure heat load
deformation due to its low amount of crystallization heat.
Comparative Example 7 shows poor tear resistance although high heat
resistance is attained by crystallization during film
formation.
TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 7 Raw materials (parts
by weight) A1 100 97 91 90 85 90 70 B1 1 1 1 1 1 1 1 C1 3 1 3 3 3 3
6 D1 1 1 1 1 1 1 1 E(a) 3 9 1 1 E(b) 10 15 E(c) 10 30 Film
thickness (.mu.m) 50 50 50 50 50 50 50 DSC data on resin Melting
temperature 172 165 165 167 167 167 167 composition Crystallization
temperature (Tc) 87 84 84 83 83 85 85 Setting temperature Resin
temperature in melt film forming step 162 162 170 162 162 162 162
(.degree. C.) Residual stress relaxing temperature 142 120 142 110
142 110 142 Crystallization promoting temperature 120 120 120 120
110 120 110 Crystallization promoting time (seconds) 30 60 30 60 30
60 60 Results of film forming Plate out to roll .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. properties Peelability .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. State of film surface .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. Tear strength (N/mm) MD 110 136 152 152
176 141 191 Amount of crystallization heat after film formation
.DELTA.Hc' (J/g) 34 36 30 33 29 29 25 Rate of dimensional change
due MD 0.2 0.0 -1.0 0.0 -0.2 -0.3 0.1 to heating (%) TD -0.2 -0.1
-0.5 -0.1 -0.3 0.0 -0.1 Rate of dimensional change due MD 2.0 0.0
0.0 2.0 1.0 1.2 2.8 to loaded heating (%)
TABLE-US-00002 TABLE 2 Comparative Example 1 2 3 4 5 6 7 8 9 Raw
materials (parts by weight) A1 100 100 100 97 94 94 90 85 85 B1 1 1
1 1 1 1 1 1 1 C1 3 3 5 6 3 2 3 4 4 D1 1 1 1 1 1 1 1 1 1 E(a) 3 6 1
1 E(b) 6 10 E(c) 15 15 Film thickness (.mu.m) 50 50 50 50 50 50 50
50 50 DSC data on Melting temperature 172 172 172 165 165 167 167
167 167 resin Crystallization temperature (Tc) 87 87 87 84 84 83 83
85 85 composition Setting Resin temperature in melt film 162 152
152 148 168 150 162 150 162 temperature forming step (.degree. C.)
Residual stress relaxing 142 142 90 120 110 120 110 120 110
temperature Crystallization promoting -- -- -- -- -- -- -- -- --
temperature Crystallization promoting time (seconds) -- -- -- -- --
-- -- -- -- Results of Plate out to roll .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle. film
forming Peelability .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. properties State of film surface
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. Tear strength (N/mm) MD 259 34 32 54 245 82 275 88
283 Amount of crystallization heat after film 18 32 35 37 17 38 17
27 15 formation .DELTA.Hc' (J/g) Rate of dimensional change MD -4.1
-1.3 -4.3 -1.2 -8.0 -1.8 -6.2 -1.7 -1.2 due to heating (%) TD -1.4
-0.1 0.5 0.1 -0.5 0.3 0.1 -0.1 -0.6 Rate of dimensional change MD
ND* -1.0 -5.2 -1.5 ND* -1.0 ND* -1.0 ND* due to loaded heating (%)
*cannot be measured because the sample is completely elongated by
load
INDUSTRIAL APPLICABILITY
[0211] The substrate in the separator according to the present
invention does not melt or deform at high temperatures more than
100.degree. C. The substrate keeps its intrinsic rigidity and does
not break or tear when tension is applied. Consequently, such a
separator is particularly useful as a separator used to protect the
surfaces of the pressure-sensitive adhesive layers of
pressure-sensitive adhesive tapes, pressure-sensitive adhesive
sheets, labels, and the like.
REFERENCE SIGNS LIST
[0212] 1 first roll [0213] 2 second roll [0214] 3 third roll [0215]
4 fourth roll [0216] 5 take-off roll [0217] 6 cooling roll [0218] 7
cooling roll [0219] 8 resin composition [0220] 9 bank (resin pool)
[0221] 10 tip of extruder
* * * * *