Method for producing fluororesin-coated roller or belt
A fluororesin coating layer fusion-bonded directly to a base member or to a rubber layer on a base member can be formed by conducting heating for a significantly short time. A fluororesin-coated roller or belt that has a fluororesin coating layer with few defects and a rubber layer underneath whose thermal deterioration is suppressed is provided. The production method therefor include a step of inserting a base member or a rubber-coated base member including a base member and at least a rubber layer on the outer peripheral surface of the base member into an empty space of a thermally shrinkable fluororesin tube; a preliminary shrinking step conducted according to need; a pressure fusion-bonding step of bringing the base member or rubber-coated base member into contact with a hot plate surface heated to a temperature in a range of 250° C. to 400° C. under pressure while rotating the base member or rubber-coated base member so as to fusion-bond the thermally shrinkable fluororesin tube onto the outer peripheral surface of the base member or the rubber-coated base member; and a reheating step and a rapid cooling step that are conducted according to need.
1. A method for producing a fluororesin-coated roller or belt that includes a base member having an outer peripheral surface having a circular cross-section taken in perpendicular to a central axis extending in a longitudinal direction and a fluororesin layer disposed directly on the base member or on a rubber layer on the base member, the method comprising:
(1) a step of inserting the base member or a rubber-coated base member prepared by forming at least a rubber layer on an outer peripheral surface of the base member into an empty space of a thermally shrinkable fluororesin tube having an inner diameter larger than an outer diameter of the base member or the rubber-coated base member;
(2) a pressure fusion-bonding step of bringing the base member or rubber-coated base member into contact with a hot plate surface heated to a temperature in a range of 250° C. to 400° C. under pressure while rotating the base member or rubber-coated base member so as to fusion-bond the thermally shrinkable fluororesin tube onto the outer peripheral surface of the base member or the rubber-coated base member;
(3) a reheating step of heating a fluororesin layer formed of the thermally shrinkable fluororesin tube fusion-bonded to the outer peripheral surface of the base member or rubber-coated base member to a temperature equal to or higher than a melting point of a fluororesin constituting the fluororesin layer; and
(4) a rapid cooling step of cooling the fluororesin layer at a rate of 200 to 600° C./min.
2. The production method according to claim 1 , further comprising a preliminary shrinking step of thermally shrinking the thermally shrinkable fluororesin tube having the base member or rubber-coated base member inserted into the empty space by controlling the temperature to 80° C. or more but not more than a melting point of the fluororesin constituting the thermally shrinkable fluororesin tube so as to bring the thermally shrinkable fluororesin tube in close contact with the outer peripheral surface of the base member or rubber-coated base member,
wherein, in the pressure fusion-bonding step, the base member or rubber-coated base member having the outer peripheral surface in close contact with the thermally shrinkable fluororesin tube is brought into contact with the hot plate surface under pressure while rotating the base member or rubber-coated base member so that the thermally shrinkable fluororesin tube is fusion-bonded to the outer peripheral surface of the base member or rubber-coated base member.
3. The production method according to claim 1 , wherein the base member is a hollow base member having a cylindrical shape, a tubular shape, or an endless-belt shape.
4. The production method according to claim 3 , wherein in the pressure fusion-bonding step,
a) a roller-shaped pressing member that has an outer diameter smaller than an inner diameter of the hollow base member is inserted into an empty space of the hollow base member; and
b) the roller-shaped pressing member is moved along the hot plate surface while applying pressing force from above onto two axial portions of the roller-shaped pressing member protruding from two end portions of the hollow base member so as to bring the base member or rubber-coated base member into contact with the hot plate surface heated to a temperature in a range of 250° C. to 400° C. under pressure while rotating the base member or rubber-coated base member,
during which the thermally shrinkable fluororesin tube is heated under pressure in a nip portion between the roller-shaped pressing member and the hot plate surface so that the thermally shrinkable fluororesin tube is fusion-bonded to the outer peripheral surface of the base member or rubber-coated base member.
5. The production method according to claim 4 , wherein the roller-shaped pressing member is moved along the hot plate surface by pitch feeding or continuously.
6. The production method according to claim 1 , wherein the thermally shrinkable fluororesin tube is a thermally shrinkable PFA tube composed of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.