Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2003-02-11
2004-03-09
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S250000, C526S253000, C526S317100, C526S348600
Reexamination Certificate
active
06703465
ABSTRACT:
The present invention relates to a fluorocopolymer which has a low fuel permeation coefficient and is excellent in the fuel barrier properties and in the adhesive properties to a non-fluorinated polymer.
A fluoropolymer (or a fluorocarbon resin) such as a polytetrafluoroethylene, a tetrafluoroethylene/perfluoro (alkyl vinyl ether) copolymer or an ethylene/tetrafluoroethylene copolymer, has excellent properties such as heat resistance, chemical resistance, weather resistance and gas barrier properties and thus is used in various fields such as semiconductor industry and automobile industry.
In recent years, an application of a fluoropolymer to a part such as a tank, a hose or a tube, particularly to a fuel hose to be used in an engine room of an automobile which is exposed to a severe condition of e.g. a high temperature environment, has been studied. A fuel hose is a hose for piping to transport a gasoline fuel containing an alcohol or an aromatic compound.
Especially, a fuel hose made of a multilayer laminate containing a fluoropolymer, has been studied as one satisfying various required properties. As the material for the inner layer which is in contact directly with a fuel, in the multilayer laminate, it is essential to use a resin which has fuel barrier properties whereby a fuel is hardly permeable, and chemical resistance to an erosive liquid such as ethanol or methanol contained in the fuel. From this viewpoint, the fluoropolymer is suitable as the material for the inner layer, since it is excellent in the heat resistance, chemical resistance and gas barrier properties. Especially, an ethylene/tetrafluoroethylene copolymer (hereinafter referred to as ETFE) is preferred as the material for the inner layer of a fuel hose, since it is excellent in fuel barrier properties.
On the other hand, as the material for the outer layer of a fuel hose, a non-fluorinated polymer excellent in the mechanical properties or durability, will be used. Usually, a polyamide resin such as polyamide 6, polyamide 11 or polyamide 12, is suitable as a non-fluorinated polymer, since it has such excellent properties.
For the above-mentioned fuel hose made of a multilayer laminate, a technique to firmly bond a layer of a fluoropolymer and a layer of a non-fluorinated polymer, is important. If the adhesive strength is inadequate, the layers are likely to peel during use, whereby a problem of clogging of the hose or an increase of the fuel permeability is likely to occur.
Accordingly, a technique to improve the interlaminar adhesion in a multilayer laminate has been studied. For example, it has been proposed to form a tube by extrusion molding of a fluoropolymer, followed by treatment of the outer surface of the fluoropolymer tube by a method such as reagent treatment, corona discharge treatment or plasma discharge treatment, to introduce various adhesive functional groups to the surface. Then, an adhesive is coated as the case requires, followed by laminating a non-fluorinated polymer on the outer side of the tube of the fluoropolymer, by extrusion. By such a method, a fuel hose excellent in the interlaminar adhesion strength can be produced. However, this method has a drawback that the process is cumbersome, and the productivity of the laminate is low. Accordingly, it is desired to develop a fluoropolymer which requires no surface treatment and which can be molded by a simple method such as co-extrusion of the fluoropolymer and a non-fluorinated polymer to obtain a fuel hose or a fuel tank, made of a multilayer laminate.
It is an object of the present invention to provide a fluorocopolymer excellent in the fuel barrier properties and in the adhesive properties to a non-fluorinated polymer, which is desired to be developed under the above-mentioned background.
The present invention provides a fluorocopolymer which comprises (A) polymerized units based on tetrafluoroethylene, (B) polymerized units based on ethylene and (C) polymerized units based on itaconic anhydride or citraconic anhydride, wherein the molar ratio of (A)/(B) is from 20/80 to 80/20, and the molar ratio of (C)/((A)+(B)) is from 1/10000 to 5/100, and which has a volume flow rate of from 1 to 1000 mm
3
/sec.
Further, the present invention provides a multilayer laminate comprising a layer of the above-mentioned fluorocopolymer and a layer of a non-fluorinated polymer, directly bonded thereto.
Still further, the present invention provides a multilayer laminate comprising a layer of the above-mentioned fluorocopolymer and a layer of a polyamide, directly bonded thereto.
Now, the present invention will be described in detail with reference to the preferred embodiments.
In the present invention, the molar ratio of (A) polymerized units based on tetrafluoroethylene (hereinafter referred to as TFE) to (B) polymerized units based on ethylene (hereinafter referred to as E), is from 20/80 to 80/20, preferably from 50/50 to 70/30, more preferably 50/50 to 60/40. If the molar ratio of (A)/(B) is too small, the heat resistance, weather resistance, chemical resistance, gas barrier properties, fuel barrier properties, etc. of the fluorocopolymer tend to decrease, and if the molar ratio is too large, the mechanical strength, melt processability, etc. tend to decrease. When the molar ratio is within this range, the fluorocopolymer will be excellent in the heat resistance, weather resistance, chemical resistance, gas barrier properties, fuel barrier properties, mechanical strength and melt processability.
(C) polymerized units based on itaconic anhydride or citraconic anhydride is such that the molar ratio of (C)/((A)+(B)) is from 1/10,000 to 5/100, preferably from 5/10,000 to 3/100, more preferably from 7/10,000 to 1/100. If the molar ratio is too small, the adhesive properties to a non-fluorinated polymer will decrease, and if it is too large, the fuel barrier properties will decrease. If it is within this range, the fluorocopolymer will be excellent in the adhesive properties and in the fuel barrier properties. Here, itaconic anhydride (hereinafter referred to as IAN) and citraconic anhydride (hereinafter referred to as CAN) may have been partially hydrolyzed before the polymerization. For example, IAN may be a mixture of IAN and itaconic acid, obtained by partial hydrolysis of IAN. Likewise, CAN may be a mixture of CAN and citraconic acid, obtained by partial hydrolysis of CAN. Further, a part of polymerized units based on IAN or CAN in the fluorocopolymer, may be hydrolyzed after the polymerization. Such polymerized units formed by the hydrolysis before or after the polymerization are regarded as a part of polymerized units (C) in the present invention. For example, the amount of polymerized units (C) represents the total amount of polymerized units based on IAN and polymerized units based on itaconic acid formed by partial hydrolysis of IAN.
If IAN or CAN is used for the production of a fluorocopolymer, it will be unnecessary to use a special polymerization method which is required in a case where maleic anhydride is employed as disclosed in JP-A-11-193312. Namely, it is preferred that an ethylene/tetrafluoroethylene copolymer having polymerized units based on acid anhydride can be obtained without using a perfluorocarboxylic acid or without copolymerizing hexafluoropropylene.
The fluorocopolymer of the present invention may contain, in addition to the polymerized units based on the above (A), (B) and (C), (D) polymerized units based on another monomer other than (A), (B) and (C).
Such another monomer may, for example, be a hydrocarbon olefin such as propylene or butene, a compound of the formula CH
2
═CX(CF
2
)
n
Y (wherein each of X and Y which are independent of each other, is a hydrogen atom or a fluorine atom, and n is an integer of from 2 to 8), a fluoroolefin having hydrogen atoms on an unsaturated group, such as vinylidene fluoride, vinyl fluoride or trifluoroethylene, a fluoroolefin having no hydrogen atom on an unsaturated group, such as hexafluoropropylene, chlorotrifluoroethylene or a perfluoro(alkyl vinyl ether) (except f
Funaki Atsushi
Nishi Eiichi
Sumi Naoko
Asahi Glass Company Limited
Lipman Bernard
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