Fluorocopolymer

Details Fluorocopolymer Fluorocopolymer

2003-02-03

2004-06-22

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...

C526S253000, C526S348800

Reexamination Certificate

active

06753393

ABSTRACT:

The present invention relates to a fluorocopolymer which has a low fuel permeation coefficient and is excellent in the fuel barrier properties.
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 to be added 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. 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.
In order to prevent air pollution due to fuels discharged from automobiles, severe regulations have been set which relate to the amount of gasoline permeated from a fuel hose. To cope with such a situation, it is required to further improve the fuel barrier properties of the material constituting a fuel hose. For this purpose, as the material constituting a fuel hose, an ethylene/tetrafluoroethylene copolymer which is excellent in the fuel barrier properties among fluoropolymers and which is excellent also in mechanical properties, is used. However, as the regulations are expected to be severer in future, it is desired to develop a fluorocopolymer having the fuel barrier properties further improved.
It is an object of the present invention to provide a fluorocopolymer excellent in the fuel barrier properties, 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 a compound represented by CH
2
═CX(CF
2
)
2
Y (wherein each of X and Y which are independent of each other, is a hydrogen atom or a fluorine atom), wherein the molar ratio of (A)/(B) is from 20/80 to 80/20, and the molar ratio of (C)/((A)+(B)) is from 1/1000 to 15/100, and which has a volume flow rate of from 1 to 1000 mm
3
/sec.
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 properties such as the heat resistance, weather resistance, chemical resistance, gas barrier properties, fuel barrier properties, mechanical strength and melt processability. In the fluorocopolymer of the present invention, the content of (C) polymerized units based on a compound (hereinafter referred to as FAE) of the above formula CH
2
═CX(CF
2
)
2
Y is such that the molar ratio of (C)/((A)+(B)) is from 1/1,000 to 15/100. When the content of (C) is within this range, the fluorocopolymer will be excellent in the fuel barrier properties and cracking resistance and is free from a breaking phenomenon such that the fluorocopolymer undergoes cracking under stress. Further, the fluorocopolymer will be excellent in strength. Such a content of (C) is preferably from 1/200 to 7/100, more preferably from 1/100 to 5/100, most preferably from 1/100 to 4/100.
FAE is a compound of the formula CH
2
═CX(CF
2
)
2
Y (wherein each of X and Y which are independent of each other, is a hydrogen atom or a fluorine atom), as mentioned above. FAE may, for example, be CH
2
═CH(CF
2
)
2
F, CH
2
═CF(CF
2
)
2
F, CH
2
═CF(CF
2
)
2
H or CH
2
═CH(CF
2
)
2
H. More preferred is CH
2
═CH(CF
2
)
2
F where X is a hydrogen atom, and Y is a fluorine atom.
The fluorocopolymer of the present invention may contain, in addition to the polymerized units based on the above (A), (B) and (C), polymerized units based on another monomer (D) other than (A), (B) and (C).
Such another monomer (D) may, for example, be a hydrocarbon olefin such as propylene or butene, a fluoroolefin having hydrogen atoms on an unsaturated group, such as vinyl fluoride or vinylidene fluoride (except for FAE), a fluoroolefin having no hydrogen atom on an unsaturated group, such as hexafluoropropylene, chlorotrifluoroethylene or a perfluoro(alkyl vinyl ether) (except for TFE), a vinyl ether such as an alkyl vinyl ether, a (fluoroalkyl) vinyl ether, glycidyl vinyl ether, hydroxybutyl vinyl ether or methyl vinyloxybutyl carbonate, a vinyl ester such as vinyl acetate or vinyl butyrate, a (meth)acrylate such as a (polyfluoroalkyl) acrylate or a (polyfluoroalkyl) methacrylate, an unsaturated carboxylic anhydride such as maleic anhydride, citraconic anhydride or itaconic anhydride, or an unsaturated carboxylic acid such as undecylenic acid, acrylic acid, methacrylic acid or maleic acid. Such another monomer may be used alone or in combination of two or more of them.
In a case where the fluorocopolymer contains polymerized units based on such another monomer (D), the content is preferably from 0.01 to 10 mol %, more preferably from 0.1 to 5 mol %, based on the total polymerized units in the fluorocopolymer.
It is preferred that the fluorocopolymer of the present invention has a molding temperature close to the molding temperature of a non-fluorinated polymer, so that it can be co-extruded with the non-fluorinated polymer to form a multilayer laminate. For this purpose, it is preferred to optimize the melting point of the fluorocopolymer by properly adjusting the proportions of (A), (B) and (C) within the above ranges. Further, it is preferred to incorporate polymerized units based on (D), since it is thereby possible to improve the co-extrusion processability with the non-fluorinated polymer by further controlling the melting point of the fluorocopolymer, or to improve the adhesive properties to other layers in the multilayer laminate. For the purpose of improving the adhesive properties, it is preferred to incorporate polymerized units based on (D) having a functional group which is reactive with the non-fluorinated polymer such as a polyamide, such as an ester group, a carbonate group, a hydroxyl group, a carboxyl group, a carboxylic anhydride residual group, a carbonyl fluoride group or an epoxy group.
Further, in the present invention, it is preferred to have, as a terminal group of the fluorocopolymer, a functional group reactive with a non-fluorinated polymer such as a polyamide, such as an ester group, a

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