Adhesive fluororesin and laminate employing it

An adhesive fluororesin (A) comprising an ethylene-tetrafluoroethylene copolymer having at least one characteristic selected from the group consisting of a melt flow characteristic which is a melt flow rate of at least 40 and an infrared absorption characteristic which is a distinct absorption peak within a wavenumber range of from 1,720 to 1,800 cm.sup.-1 in its infrared absorption spectrum.

The present invention relates to a laminate comprising a layer of a 
fluororesin made of a specific ethylene-tetrafluoroethylene copolymer, 
particularly a laminate excellent in the adhesive strength between that 
layer and another layer. 
A fluororesin made of an ethylene-tetrafluoroethylene copolymer (ETFE) is 
excellent in chemical resistance, weather resistance, surface properties, 
etc., and is used in a wide range of fields. For example, a film of ETFE 
is used as a surface covering material for a substrate made of an 
inorganic material such as a metal or glass or an organic material such as 
a synthetic resin. A thermoplastic resin laminate is produced usually by 
directly overlaying and bonding thermoplastic resin layers one on another 
by e.g. coextrusion molding or heat fusion. However, in a case of a 
laminate made of resins having substantially different properties, the 
interlaminar bond strength of such a laminate has been inadequate. 
Particularly in a case of a multilayer film or a multilayer tube prepared 
by laminating ETFE and other thermoplastic resins by a coextrusion molding 
method or a heat fusion method, the interlaminar bond strength has not 
been adequate. 
It is an object of the present invention to provide an adhesive fluororesin 
and a laminate wherein such a fluororesin layer and a thermoplastic resin 
layer are directly firmly bonded to each other. 
The present invention provides an adhesive fluororesin (A) comprising an 
ethylene-tetrafluoroethylene copolymer (hereinafter referred to as ETFE 
(A)) having at least one characteristic among a melt flow characteristic 
that its melt flow rate is at least 40 and an infrared absorption 
characteristic that it has a distinct absorption peak within a wavenumber 
range of from 1,720 to 1,800 cm.sup.-1 in its infrared absorption 
spectrum. 
Further, the present invention provides a laminate comprising a layer of 
this ETFE (A) and a layer of a thermoplastic resin (B) other than ETFE 
(A), said layers being in contact directly with each other. 
The present invention also provides an adhesive fluororesin (A) comprising 
an ethylene-tetrafluoroethylene copolymer having a melt flow 
characteristic that its melt flow rate is at least 40 and an infrared 
absorption characteristic that it has a distinct absorption peak within a 
wavenumber range of from 1,720 to 1,800 cm.sup.-1 in its infrared 
absorption spectrum (one type of ETFE (A)). 
Further, the present invention provides a laminate comprising a layer of 
this ETFE (A) and a layer of a thermoplastic resin (B) other than ETFE 
(A), said layers being in contact directly with each other. 
In the present invention, the melt flow rate of ETFE (A) is a value 
measured by the method stipulated in ASTM D-3159. Namely, when ETFE (A) is 
used alone, the melt flow rate corresponds to its amount (g/10 min) which 
passes through a nozzle having a diameter of 2 mm and a length of 10 mm 
for 10 minutes under a load of 5 kg at a temperature of 297.degree. C. 
Further, in the present invention, "it has a distinct absorption peak 
within a wavenumber range of from 1,720 to 1,800 cm.sup.-1 in its infrared 
absorption spectrum" means that when a sample having a thickness of 100 
.mu.m, made of the resin alone, is used for measurement of the infrared 
absorption spectrum, the absorption peak with an absorbance of at least 
0.002 is present within a wavenumber range of from 1,720 to 1,800 
cm.sup.-1. 
The melt flow rate (hereinafter referred to as MFR) is an index of the melt 
flow characteristic and also an index of the molecular weight. Usually, 
MFR of ETFE obtainable by polymerization is less than 40 (e.g. MFR of 
AFLON LF-740AP (sold by Asahi Glass Company Ltd.) which is commercially 
available ETFE, is 38). ETFE (A) having a MFR of at least 40 provides a 
high bond strength even to a material which used to have no adequate bond 
strength or used to be impossible to bond. More preferably, MFR of ETFE 
(A) is at least 50, particularly preferably at least 60. The upper limit 
of MFR of ETFE (A) is not particularly limited and may substantially be 
infinite (i.e. a liquid at a temperature of 297.degree. C.). However, it 
is required to be a solid having a bond strength at a practical 
temperature for use of the laminate of the present invention. 
Further, ETFE (A) having the infrared absorption characteristic of the 
present invention exhibits a high bond strength to a material which used 
to have no adequate bond strength or used to be impossible to bond. 
Especially, ETFE (A) having a distinct absorption peak at a wavenumber of 
1,759 cm.sup.-1 or 1,788 cm.sup.-1, is preferred, since it remarkably 
increases the bond strength with other materials. 
Especially, ETFE (A) which has a MFR of at least 40 and the infrared 
absorption characteristic of the invention, is particularly preferred, 
since it exhibits a practically sufficiently high bond strength even to a 
material which used to have no adequate bond strength or used to be 
impossible to bond. 
ETFE is a copolymer obtained by copolymerizing tetrafluoroethylene 
(hereinafter referred to as TFE) and ethylene, or a copolymer obtained by 
copolymerizing these monomers with at least one other monomer 
copolymerizable with these monomers. A copolymer is preferred wherein the 
molar ratio of polymer units derived from TFE/polymer units derived from 
ethylene/polymer units derived from other monomers is 70 to 35/25 to 60/0 
to 40. Particularly preferred is a copolymer wherein the molar ratio is 65 
to 50/30 to 45/0 to 10. 
Said other monomers copolymerizable with TFE and ethylene, may, for 
example, be .alpha.-olefins such as propylene and butene, fluoroolefins 
having hydrogen atoms directly bonded to a polymerizable unsaturated 
group, such as vinylidene fluoride and (perfluorobutyl)ethylene, vinyl 
ethers such as an alkyl vinyl ether and a (fluoroalkyl) vinyl ether, 
(meth)acrylates such as a (fluoroalkyl) methacrylate and a (fluoroalkyl) 
acrylate, and perfluoromonomers having no hydrogen atom bonded to a 
polymerizable unsaturated group, such as hexafluoropropylene and perfluoro 
(alkyl vinyl ether). 
ETFE (A) having a MFR of at least 40 can be produced by the following 
methods. 
A first method is a method of producing ETFE (A) having a MFR of at least 
40 directly by polymerization. For example, in a case where it is produced 
by suspension polymerization, it is possible to obtain ETFE (A) having a 
MFR of at least 40 by adding a chain transfer agent to an aqueous medium 
using a hydrocarbon type peroxide as an initiator, and adjusting the type 
or the amount of the chain transfer agent to adjust the molecular weight 
of the resulting polymer (namely to obtain a polymer having a lower 
molecular weight than usual ETFE). For the production of ETFE (A), various 
conventional polymerization methods such as bulk polymerization, 
suspension polymerization, emulsion polymerization and solution 
polymerization, may be employed. ETFE (A) obtained by the above 
polymerization does not usually have the infrared absorption 
characteristic of the present invention. 
A second method is a method to bring MFR to at least 40 by creating 
breakage of the molecular chains of ETFE obtained by a conventional 
polymerization method (ETFE having a MFR of less than 40) to lower the 
molecular weight. For example, ETFE may be subjected to heat treatment or 
irradiation with high energy rays such as radio active rays, ultraviolet 
rays or low temperature plasma to obtain such a product. By carrying out 
such treatment in the presence of an oxygen in the treatment atmosphere, 
it is possible to obtain ETFE (A) having a MFR of at least 40 effectively. 
Treatment in an atmosphere having a higher oxygen concentration, is 
effective. Usually, the treatment is carried out in an air atmosphere. In 
the case of heat treatment, the desired ETFE (A) can be obtained by 
heating ETFE, for example, in air at a temperature of at least 300.degree. 
C. for at least 3 minutes, preferably at a temperature of from 330 to 
400.degree. C. for from 5 to 30 minutes. Usual ETFE has a melting point of 
about 300.degree. C. Accordingly, this treatment is carried out usually at 
a temperature of at least the melting point of non-treated ETFE. 
A third method is a method to bring MFR to at least 40 by creating breakage 
of the molecular chains of ETFE by free radicals to lower the molecular 
weight. For example, ETFE having a MFR of less than 40 and a peroxide are 
melt-kneaded to break the molecular chains of ETFE by free radicals 
generated from the peroxide to lower the molecular weight, thereby to 
obtain ETFE (A) having a MFR of at least 40. The treating temperature is 
at least a temperature at which the peroxide will decompose to form free 
radicals, and it is usually at least 120.degree. C. For the melt kneading, 
a temperature of at least the melting point of ETFE is employed. The 
temperature for this treatment is preferably from the melting point of 
ETFE to 350.degree. C. 
As the peroxide, ketone peroxides, dialkyl peroxides such as 
2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, diacyl peroxides such as 
benzoyl peroxide, peroxydicarbonates such as diisopropyl 
peroxydicarbonate, alkyl peresters such as t-butylperoxy isobutyrate, and 
hydroxyperoxides such as t-butylhydroxyperoxide, may, for example, be 
used. 
As starting material ETFE to be used in these second and third methods, 
ETFE having a MFR of less than 40, may be employed, but the material is 
not limited thereto. For example, ETFE having a MFR of at least 40, such 
as ETFE (A) obtained by the first method may be subjected to the second or 
third method to further increase MFR. 
The infrared absorption characteristic of ETFE (A) in the present invention 
is considered to be a characteristic attributable to the presence of 
functional groups in ETFE (A), which correspond to the distinct absorption 
peak within a wavenumber range of from 1,720 to 1,800 cm.sup.-1 in its 
infrared absorption spectrum. Such functional groups are not present in 
ETFE obtained by a usual polymerization method. Such functional groups are 
considered to be functional groups which are formed by the reaction with 
oxygen atoms, of double bonds formed anew in the molecular chains by a 
reaction to withdraw hydrogen atoms or fluorine atoms from ETFE. 
Accordingly, for example, among the above-mentioned methods for obtaining 
ETFE (A) having a MFR of at least 40, the second or third method may be 
employed to produce ETFE (A) having this infrared absorption 
characteristic. Namely, by such a method, double bonds may be introduced 
into the molecular chains of ETFE, and at the same time, oxygen atoms are 
reacted to such double bonds to form ETFE having the above functional 
groups. 
When ETFE (A) having the infrared absorption characteristic is produced by 
the second method, it is particularly preferred to carry out the heat 
treatment or the high energy ray irradiation in an oxygen-containing 
atmosphere. Particularly preferred is a method of heating ETFE in air at a 
temperature of at least 300.degree. C. for at least 3 minutes, preferably 
at a temperature of from 330 to 400.degree. C. for from 5 to 30 minutes. 
When ETFE (A) having the infrared absorption characteristic is produced by 
the third method, it is preferred to employ a method of melting and 
kneading ETFE and the peroxide. Particularly preferred is a method of 
melting and kneading the starting material ETFE and the peroxide at a 
temperature of from the melting point of ETFE to 350.degree. C. It is 
considered that by these methods, the oxygen in the atmosphere or free 
radicals derived from the peroxide (or both the oxygen in the atmosphere 
and the free radicals) will contribute to formation of the above 
functional groups. The starting material ETFE for these methods, may be 
ETFE having a MFR of less than 40 or ETFE having a MFR of at least 40. 
ETFE (A) having a MFR of at least 40 and the infrared absorption 
characteristic, can be produced by the above-mentioned second or third 
method, as described above. Such a method is not only a method capable of 
producing ETFE (A) having a MFR of at least 40, but also a method capable 
of producing ETFE (A) having the infrared absorption characteristic. 
Particularly preferred is a method for carrying out heat treatment of ETFE 
in air at a temperature of at least 300.degree. C. for at least 3 minutes, 
preferably at a temperature of from 330 to 400.degree. C. for from 5 to 30 
minutes, or a method for melting and kneading ETFE and the peroxide at a 
temperature of from the melting point of ETFE to 350.degree. C. 
As the thermoplastic resin (B) other than ETFE (A), various thermoplastic 
resins may be used. Further, it may be a thermoplastic resin having 
flexibility, so-called a thermoplastic elastomer. Or, it may be a mixture 
of different thermoplastic resins. As such a thermoplastic resin, 
specifically, the following thermoplastic resins may, for example, be 
mentioned: 
A fluororesin other than ETFE (A), a polyolefin resin, a polyamide resin, a 
polyester resin, a polystyrene resin, an ABS resin, a BS resin, a MBS 
resin, an EVA resin, an acrylic resin, a polyurethane resin, a polyimide 
resin, a polyphenylenesulfide resin, a vinyl chloride resin, a polyolefin 
type thermoplastic elastomer, a polyamide type thermoplastic elastomer, a 
polyester type thermoplastic elastomer, a polybutadiene type thermoplastic 
elastomer, a polystyrene type thermoplastic elastomer, a polyvinyl 
chloride thermoplastic elastomer and a fluorine-containing thermoplastic 
elastomer. 
More specifically, the following thermoplastic resins may, for example, be 
mentioned; ETFE other than ETFE (A), a fluororesin such as PFA or FEP, a 
polyolefin resin such as polyethylene or polypropylene, a polyamide resin 
such as polyamide 6, polyamide 11 or polyamide 12, a polyester resin such 
as polyethylene terephthalate or polybutylene terephthalate, and an 
acrylic resin such as polymethyl methacrylate. 
Preferred as the thermoplastic resin (B) is a polyamide type thermoplastic 
resin such as a polyamide resin or a polyamide type thermoplastic 
elastomer. Particularly preferred is a polyamide resin such as polyamide 
6, polyamide 11 or polyamide 12. Such a polyamide type thermoplastic resin 
has a relatively small penetrability of a fuel oil. 
To the respective resins constituting the layers of the laminate of the 
present invention, various additives may be incorporated, as the case 
requires. Such additives are preferably not to impair the required 
performance of such layers. For example, so long as the predetermined 
adhesive properties can be maintained, various additives may be 
incorporated to ETFE (A). Such additives include, for example, a filler, 
reinforcing fibers, a pigment, a plasticizer, a tackifier, a silane 
coupling agent and a titanate type coupling agent. Further, so long as the 
predetermined adhesive property can be maintained, other resins may be 
incorporated to ETFE (A), and for example, usual ETFE may be incorporated. 
The laminate of the present invention is a laminate wherein a layer of ETFE 
(A) (hereinafter referred to as layer (A)) and a layer of a thermoplastic 
resin (B) (hereinafter referred to as layer (B)) are in contact directly 
with each other. The laminate of the present invention is not limited to 
the double layer structure comprising layer (A) and layer (B). So long as 
it contains a double layer structure wherein layer (A) and layer (B) are 
in contact directly with each other (hereinafter referred to as layers 
(A)/(B)), it may be a laminate having a structure of three or more layers. 
On the layer (A) side of layers (A)/(B), at least one layer made of a 
resin which may be the same as or different from the resin of layer (A), 
may be formed. ETFE (A) of layer (A) may be bonded to not only the same 
resin but also to a different resin such as the thermoplastic resin (B) 
with a high bond strength as mentioned above. Similarly, on the layer (B) 
side of layers (A)/(B), at least one layer made of a resin which is the 
same as or different from the resin of layer (B) may be formed. Further, 
in some cases, the layer which is in contact with layer (A) or layer (B) 
may be made of a material other than a resin. A preferred other layer is a 
layer of a thermoplastic resin. 
When a third layer is present on the layer (A) side of layers (A)/(B), such 
a layer will hereinafter be referred to as layer (C). The material for 
layer (C) which is in direct contact with layer (A) is preferably a 
thermoplastic resin similar to the thermoplastic resin (B). However, the 
material is not limited thereto and may be made of a resin other than a 
thermoplastic resin or a material other than a resin. A preferred material 
for layer (C) is a thermoplastic fluororesin, and particularly preferred 
is ETFE other than ETFE (A). Further, it is preferred that layer (C) is 
made of the same resin (i.e. ETFE (A)) as layer (A) or it is a layer of a 
resin having different physical properties (for example, layer (A) is a 
layer composed solely of ETFE (A), and layer (C) is a layer comprising 
ETFE (A) and the after-mentioned conductive additive and having electrical 
conductivity). To the thermoplastic resin of layer (C), the 
above-mentioned various additives may be incorporated. 
The laminate of the present invention is useful particularly as a tube for 
transporting a fuel or a container for storage of a fuel. ETFE including 
ETFE (A) has high chemical resistance against a liquid fuel such as 
gasoline and further has a characteristic such that the penetrability of a 
liquid fuel is particularly small as compared with other thermoplastic 
fluororesins. Accordingly, in a case where the layer contacting a liquid 
fuel is a layer of ETFE (A) or ETFE, the interlaminar bond strength of the 
laminate is less likely to be affected by penetration of a liquid fuel, 
and the initial high bond strength can be maintained. Accordingly, the 
layer made of a resin such as ETFE (A) or ETFE is preferably a surface 
layer which is in contact directly with the liquid fuel, or a layer close 
to the surface. In such use, if ETFE is used alone, the physical strength 
or the like tends to be inadequate, and such a problem can be solved by 
the laminate of the present invention wherein a layer (B) supplementing 
such a physical property is incorporated. 
In the above use, a part of the layer of the laminate, particularly the 
surface layer which is in contact with a fuel, is required to be a layer 
having electrical conductivity and having an antistatic function 
(hereinafter referred to as a conductive layer) in many cases. In order to 
provide the antistatic function, the volume resistivity of the material 
for the conductive layer is preferably within a range of from 
1.times.10.sup.0 to 1.times.10.sup.9 .OMEGA.cm, particularly from 
1.times.10.sup.2 to 1.times.10.sup.9 .OMEGA.cm. In order to make a resin 
layer to be a conductive layer, it is preferably a resin layer containing 
a conductive additive. In order to bring the volume resistivity of the 
resin containing the conductive additive within this range, it is 
preferred that the conductive additive is contained in an amount of from 1 
to 30 parts by weight, particularly from 5 to 20 parts by weight, per 100 
parts by weight of the resin, although it may depend upon the conductive 
additive or the type of the resin. 
The conductive additive may, for example, be a powder or fibers of a metal 
or carbon, a powder of a conductive compound such as zinc oxide, or a 
non-conductive powder having the surface treated for electrical 
conductivity by e.g. metallizing. As the powder or fibers of a metal or 
carbon, a powder of a metal such as copper, nickel or silver, fibers of a 
metal such as iron or stainless steel, carbon black, or carbon fibers, 
may, for example, be mentioned. As the non-conductive powder treated for 
electrical conductivity, a metallized inorganic compound powder having the 
surface of glass beads or titanium oxide metallized by metal sputtering or 
electroless plating, may, for example, be mentioned. 
As mentioned above, the laminate of the present invention having a 
conductive layer is preferably such that the surface layer which will be 
in contact with a liquid fuel or a layer close thereto, is made of a resin 
such as ETFE and is a conductive layer. Accordingly, in the case of a 
laminate composed of two layers of layers (A)/(B), it is preferred that 
layer (A) is the surface layer which will be in contact with a liquid fuel 
and is a conductive layer. In the case of a laminate wherein layer (C) is 
present on the layer (A) side of layers (A)/(B), and layer (C) is a 
surface layer which will be in contact with a liquid fuel, it is preferred 
that layer (C) is a conductive layer. Particularly preferably, layer (C) 
is made of a fluororesin such as ETFE (A) or ETFE and is a conductive 
layer. Most preferably, layer (C) is made of ETFE and is a conductive 
layer. In these cases, the material for layer (B) is preferably a 
polyamide type thermoplastic resin as mentioned above, from the viewpoint 
of e.g. the required performance of physical strength. 
Further, by means of ETFE (A) of the present invention, a film or the like 
made of a fluororesin other than ETFE (A), may, for example, be bonded to 
cover the surface of a substrate made of an organic material such as a 
metal or glass or an organic material such as a synthetic resin. 
The thickness of each layer of the laminate of the present invention is not 
particularly limited, but is preferably within a range of from 0.05 to 2.0 
mm. In a case where layer (C) is present on the layer (A) side of layers 
(A)/(B), particularly in a case where the material of layer (C) is ETFE 
other than ETFE (A), it is preferred that the thickness of layer (A) is 
thicker than the thickness of layer (C) in order to improve the bond 
strength between layer (A) and layer (C). 
The shape of the laminate of the present invention is not particularly 
limited, but is preferably a film-like laminate or a tubular laminate. In 
the case of a tubular laminate, the thickness of each layer is preferably 
within the above range, and the outer diameter of the tube is preferably 
from 5 to 30 mm, and the inner diameter is preferably from 3 to 25 mm. As 
the method for producing the laminate of the present invention, a 
coextrusion molding method is preferred wherein the laminate is produced 
by coextrusion molding. However, the method for the production is not 
limited thereto, and it may be produced by various methods such as a heat 
fusion method wherein films, sheets or tubes made of materials forming the 
respective layers are laminated and pressed for heat fusion.

Now, the present invention will be described in further detail with 
reference to Examples. However, it should be understood that the present 
invention is by no means restricted to such specific Examples. In the 
Examples, "parts" means "parts by weight". Further, the infrared 
absorption characteristics of the resins in Preparation Examples, were 
measured by means of films having a thickness of 100 .mu.m formed from 
pellets produced in the Preparation Examples. 
Preparation Example 1 
Into a 100 l reactor, a mixed medium comprising 27 kg of water and 42 kg of 
perfluorocyclohexane, 5.5 kg of TFE, 0.2 kg of ethylene, 0.5 kg of 
(perfluorobutyl)ethylene and 0.5 kg of acetone as a chain transfer agent, 
were charged, and the temperature was raised to 65.degree. C. Then, 300 ml 
of a perfluorohexane solution containing 10 wt % of t-butyl 
peroxyisobutyrate as a polymerization initiator, was added thereto to 
initiate suspension polymerization. During the polymerization, a mixed gas 
of TFE/ethylene (molar ratio: 60/40) was supplied to maintain the pressure 
constant. When the supplied amount of the mixed gas reached 8 kg, the 
polymerization was terminated. 
The slurry was subjected to filtration and drying to obtain polymer A 
having a molar ratio of polymer units derived from ethylene/polymer units 
derived from TFE/polymer units derived from 
(perfluorobutyl)ethylene=58/39/3. Then, polymer A was pelletized by means 
of a single screw extruder at a temperature of 270.degree. C. for a 
retention time of 3 minutes to obtain pellets 1. MFR of the resin of 
pellets 1 was 72. Further, no absorption peak was observed at a wavenumber 
of from 1,720 to 1,800 cm.sup.-1. 
Preparation Example 2 
Polymer B was prepared in the same manner as in Preparation Example 1 
except that the amount of acetone as the chain transfer agent was changed 
to 0.2 kg. Polymer B had a molar ratio of polymer units derived from 
ethylene/polymer units derived from TFE/polymer units derived from 
(perfluorobutyl)ethylene=58.5/39.0/2.5. Then, polymer B was pelletized by 
means of a single screw extruder at a temperature of 265.degree. C. for a 
retention time of 2 minutes to obtain pellets 2. MFR of the resin of 
pellets 2 was 26. Further, no absorption peak was observed at a wavenumber 
of from 1,720 to 1,800 cm.sup.-1. FIG. 1 shows infrared absorption 
spectrum of the resin. 
Preparation Example 3 
100 Parts of pellets 2 were subjected to heat treatment in an oven of 
350.degree. C. for 60 minutes. Then, the heat treated product was 
pelletized by means of a single screw extruder at a temperature of 
270.degree. C. for a retention time of 3 minutes to obtain pellets 3. MFR 
of the resin of pellets 3 was 83. Further, absorbance of 0.058 was 
observed at a wavenumber of 1,759 cm.sup.-1, and absorbance of 0.008 was 
observed at 1,788 cm.sup.-1. FIG. 2 shows the infrared absorption spectrum 
of the resin. 
Preparation Example 4 
A mixture comprising 100 parts of pellets 2 and 0.2 part of t-butyl 
hydroperoxide, was pelletized by melt kneading by means of a twin screw 
extruder at a temperature of 310.degree. C. for a retention time of 5 
minutes to obtain pellets 4. MFR of the resin of pellets 4 was 64, and 
absorbance of 0.040 was observed at 1,759 cm.sup.-1, and absorbance of 
0.016 was observed at 1,788 cm.sup.-1. FIG. 3 shows the infrared 
absorption spectrum of the resin. 
Preparation Example 5 
100 Parts of pellets 2 and 20 parts of carbon black as a conductive 
additive (Denka Black, manufactured by Denki Kagaku Kogyo K.K.) were 
preliminarily mixed and pelletized by melt-kneading by means of a twin 
screw extruder at a temperature of 270.degree. C. for a retention time of 
3 minutes to obtain pellets 5. The volume resistivity of the resin of 
pellets 5 was 2.1.times.10.sup.3 .OMEGA.cm. Further, MFR of the resin 
obtained by melt-kneading pellets 2 under the above conditions without 
mixing carbon black, was 26, and no absorption peak was observed at a 
wavenumber of from 1,720 to 1,800 cm.sup.-1. 
Preparation Example 6 
A granulated powder (average particle size: 1 to 2 mm) of polymer B was 
subjected to corona discharge treatment in air with an output of 1.2 kW 
and then pelletized by means of a single screw extruder at a temperature 
of 260.degree. C. for a retention time of 2 minutes to obtain pellets 6. 
MFR of the resin of pellets 6 was 24, and absorbance of 0.035 was observed 
at 1,759 cm.sup.-1, and absorbance of 0.004 was observed at 1,788 
cm.sup.-1. 
Preparation Example 7 
100 Parts of pellets 1 and 20 parts of carbon black as a conductive 
additive (Denka Black, manufactured by Denki Kagaku Kogyo K.K.) were 
preliminarily mixed and pelletized by melt-kneading by means of a twin 
screw extruder at a temperature of 350.degree. C. for a retention time of 
3 minutes to obtain pellets 7. The volume resistivity of the resin of 
pellets 7 was 1.6.times.10.sup.2 .OMEGA.cm. Further, MFR of the resin 
obtained by melt-kneading pellets 1 under the above conditions without 
mixing carbon black, was 52, and absorbance of 0.039 was observed at 1,759 
cm.sup.-1, and absorbance of 0.005 was observed at 1,788 cm.sup.-1. 
EXAMPLE 1 
A laminated tube having a three layer structure was produced by means of a 
coextrusion molding machine. Pellets 1 were supplied to a cylinder for 
forming an interlayer of the tube and transported to a transport zone of 
the cylinder after a retention time of 3 minutes in a melting zone of the 
cylinder at a temperature of 270.degree. C. Pellets of polyamide 12 
(L-2121, manufactured by Daicel Huls K.K.) (hereinafter referred to as 
pellets 8) were supplied to a cylinder for forming an outer layer of the 
tube. Further, pellets 5 were supplied to a cylinder for forming an inner 
layer. By setting the temperatures of the transport zones of the cylinders 
for pellets 8 and pellets 5 to be 240.degree. C. and 270.degree. C., 
respectively, the retention times to be 2 minutes and 3 minutes, 
respectively, and the temperatures of coextrusion die to be 260.degree. 
C., a laminated tube of a three layer structure comprising an outer layer 
made of the material of pellets 8, an interlayer made of the material of 
pellets 1 and an inner layer made of the material of pellets 5, was 
molded. 
The outer diameter of the laminated tube was 8 mm, the inner diameter was 6 
mm, and the thicknesses of the outer layer, the interlayer and the inner 
layer were 0.75 mm, 0.15 mm and 0.10 mm, respectively. Further, the peel 
strength between the outer layer and the interlayer was 7.2 kg/cm, and the 
volume resistivity of the conductive layer of the inner layer was 
3.2.times.10.sup.2 .OMEGA.cm. Further, the obtained tube was immersed in a 
fuel oil (fuel oil C in accordance with JIS K6301 (isooctane/toluene=50/50 
(volume ratio)), the same applies hereinafter) at 60.degree. C. for 240 
hours, and thereafter, the peel strength between the outer layer and the 
interlayer was measured and found to be 5.8 kg/cm, and no peeling was 
possible at the interface between the inner layer and the interlayer. 
Thus, this laminated tube had properties suitable particularly as a 
laminated tube for transporting a liquid fuel. 
EXAMPLE 2 
A laminated film having a double layer structure was produced by means of a 
coextrusion molding machine in the same manner as in Example 1. Pellets 3 
were supplied to a cylinder for forming a first layer of the film, and 
pellets of polyamide 11 (RILSAN AESN 20 TL, manufactured by Toray 
Corporation) (hereinafter referred to as pellets 9) were supplied to a 
cylinder for forming the other layer. The temperatures at the transport 
zones of the cylinders for pellets 3 and pellets 9 were 265.degree. C. and 
240.degree. C., respectively, the retention times were 2 minutes and 3 
minutes, respectively, and the temperature of the coextrusion die was 
255.degree. C. By this molding, a laminated film comprising a layer made 
of the material of pellets 9 and a layer made of the material of pellets 
3, was obtained. The thickness of the layer made of the material of 
pellets 9 was 0.60 mm and the thickness of the layer made of the material 
of pellets 3 was 0.10 mm. The interlaminar peel strength was 6.1 kg/cm. 
EXAMPLE 3 
A laminated tube of a three layer structure was produced by means of a 
coextrusion molding machine in the same manner as in Example 1. Pellets 4 
were supplied to a cylinder for forming an interlayer of the tube and 
transported to a transport zone of the cylinder after a retention time of 
3 minutes in a melting zone of the cylinder at 270.degree. C. Pellets of 
polyamide 12 (L-2140, manufactured by Daicel Huls K.K.) (hereinafter 
referred to as pellets 10) were supplied to a cylinder for forming an 
outer layer of the tube. Further, pellets 5 were supplied to a cylinder 
for forming an inner layer. By setting the temperatures at the transport 
zones of the cylinders for pellets 10 and pellets 5 to be 240.degree. C. 
and 270.degree. C., respectively, the retention times to be 2 minutes and 
3 minutes, respectively, and the temperature of coextrusion die to be 
260.degree. C., a laminated tube of a three layer structure was molded. 
This tube comprised an outer layer made of the material of pellets 10, an 
interlayer made of the material of pellets 4, and an inner layer made of 
the material of pellets 5. 
The outer diameter of the laminated tube was 8 mm, the inner diameter was 6 
mm, and the thicknesses of the outer layer, the interlayer and the inner 
layer were 0.75 mm, 0.15 mm and 0.10 mm, respectively. The peel strength 
between the outer layer and the interlayer was 7.2 kg/cm, and the volume 
resistivity of the conductive layer of the inner layer was 
3.2.times.10.sup.2 .OMEGA.cm. Further, the obtained laminated tube was 
immersed in a fuel oil at 60.degree. C. for 240 hours, and thereafter, the 
peel strength between the outer layer and the interlayer was measured and 
found to be 5.8 kg/cm, and no peeling was possible at the interface 
between the inner layer and the interlayer. Thus, this laminated tube had 
properties suitable particularly as a laminated tube for transporting a 
liquid fuel. 
EXAMPLE 4 
A laminated film of a double layer structure was produced by means of a 
coextrusion molding machine in the same manner as in Example 2. Pellets 6 
were supplied to a cylinder for forming a first layer of the film, and 
pellets of polyamide 6 (BM1042, manufactured by Toray Corporation) 
(hereinafter referred to as pellets 11) were supplied to a cylinder for 
forming the other layer. By setting the temperatures at the transport 
zones of the cylinders for pellets 6 and pellets 11 to be 265.degree. C. 
and 260.degree. C., respectively, the retention times to be 2.5 minutes 
and 3 minutes, respectively, and the coextrusion die temperature to be 
260.degree. C., a laminated film comprising a layer made of the material 
of pellets 11 and a layer made of the material of pellets 6, was molded. 
The thickness of the layer made of the material of pellets 11 was 0.80 mm, 
and the thickness of the layer made of the material of pellets 6 was 0.20 
mm, and the interlaminar peel strength was 2.9 kg/cm. 
EXAMPLE 5 
A laminated tube of a double layer structure was produced by means of a 
coextrusion molding machine in the same manner as in Example 1. Pellets 7 
were supplied to a cylinder for forming an inner layer of the tube, and 
pellets 8 were supplied to a cylinder for forming an outer layer. By 
setting the temperatures at the transport zones of the cylinders for 
pellets 7 and pellets 8 to be 280.degree. C. and 240.degree. C., 
respectively, the retention times to be 3 minutes and 2 minutes, 
respectively, and the temperature of the coextrusion die to be 260.degree. 
C., a laminated tube of a double layer structure comprising an inner layer 
made of the material of pellets 7 and an outer layer made of the material 
of pellets 8, was molded. 
The outer diameter of the laminated tube was 8 mm, the inner diameter was 6 
mm, and the thicknesses of the outer layer and the inner layer were 0.80 
mm and 0.20 mm, respectively. The peel strength between the outer layer 
and the inner layer was 4.8 kg/cm, and the volume resistivity of the 
conductive layer of the inner layer was 8.5.times.10.sup.3 .OMEGA.cm. 
Further, the obtained tube was immersed in a fuel oil at 60.degree. C. for 
720 hours, and thereafter, the peel strength between the outer layer and 
the inner layer was measured and found to be 4.6 kg/cm. Thus, this 
laminated tube had properties particularly suitable as a laminated tube 
for transporting a liquid fuel. 
EXAMPLE 6 
Comparative Example 
A laminated tube of a three layer structure was produced by means of a 
coextrusion molding machine in the same manner as in Example 1. Pellets 2 
were supplied to a cylinder for forming an interlayer of the tube and 
transported to the transport zone of the cylinder after a retention time 
of 3 minutes at the melt zone temperature of the cylinder being 
270.degree. C. Pellets 8 were supplied to a cylinder for forming an outer 
layer of the tube. Further, pellets 5 were supplied to a cylinder for 
forming an inner layer. By setting the temperatures at the transport zones 
of the cylinders for pellets 8 and pellets 5 to be 240.degree. C. and 
270.degree. C., respectively, the retention times to be 2 minutes and 3 
minutes, respectively, and the temperature of the coextrusion die to be 
260.degree. C., a laminated tube of a three layer structure, was molded. 
This tube comprised an outer layer made of the material of pellets 8, an 
interlayer made of the material of pellets 2, and an inner layer made of 
the material of pellets 5. 
The outer diameter of this laminated tube was 8 mm, the inner diameter was 
6 mm, and the thicknesses of the outer layer, the interlayer and the inner 
layer were 0.75 mm, 0.15 mm and 0.10 mm, respectively. Further, the peel 
strength between the outer layer and the interlayer was not higher than 
0.1 kg/cm.sup.2, and the volume resistivity of the conductive layer of the 
inner layer was 3.4.times.10.sup.2 .OMEGA.cm. Further, this laminated tube 
was immersed in a fuel oil at 60.degree. C. for 240 hours, and thereafter, 
the peel strength between the outer layer and the interlayer was measured 
and found to be not higher than 0.1 kg/cm. 
EXAMPLE 7 
Comparative Example 
A laminated film of a double layer structure was produced by means of a 
coextrusion molding machine in the same manner as in Example 1. Pellets 2 
were supplied to a cylinder for forming a first layer of the film, and 
pellets 10 were supplied to a cylinder for forming the other layer. By 
setting the temperatures at the transport zones of the cylinders for 
pellets 2 and pellets 10 to be 265.degree. C. and 260.degree. C., 
respectively, the retention times to be 2.5 minutes and 3 minutes, 
respectively, and the temperature of the coextrusion die to be 260.degree. 
C., a laminated film comprising a layer made of the material of pellets 2 
and a layer made of the material of pellets 10, was prepared. The 
thickness of the layer made of the material of pellets 10 was 0.75 mm, and 
the thickness of the layer made of the material of pellets 2 was 0.25 mm. 
The interlaminar peel strength was not higher than 0.1 kg/cm. 
As described in the foregoing, a layer of a fluororesin (A) comprising ETFE 
having a melt flow characteristic of MFR being at least 40 and/or the 
infrared absorption characteristic, is capable of firmly bonding to a 
layer of a thermoplastic resin (B) such as a polyamide resin and capable 
of maintaining its high bond strength even when contacted with a liquid 
fuel. A laminate having a layer of such fluororesin (A) and a layer of a 
thermoplastic resin (B), or a laminate having at least three layer 
structure having an ETFE layer further formed on the fluororesin (A) layer 
side, has properties suitable as a tube for transporting a liquid fuel 
such as gasoline, by virtue of the high interlaminar bond strength and the 
property not to permit penetration of a liquid fuel which is specific to 
ETFE. Further, in such use, the surface layer which is in contact with a 
liquid fuel may be made to be a conductive layer to present an antistatic 
property.