EP1416071A1

EP1416071A1 - Method of producing electrothermal filament containing carbon black and the product of the method

Info

Publication number: EP1416071A1
Application number: EP02024120A
Authority: EP
Inventors: Shih-Yuan Lee
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-10-28
Filing date: 2002-10-29
Publication date: 2004-05-06
Also published as: US20040081826A1

Abstract

A method of producing electrothermal filament containing carbon black that first grafts carbon black to monomer to form grafted copolymer. Then, the grafted copolymer is coated around the filament to form a conductive core. Lastly, membrane is laminated around the conductive core to protect and insulate the core.

Description

1. Field of the Invention

The present invention relates to a method of producing electrothermal filament and the electrothermal filaments themselves, and more particularly a method of producing electrothermal filament containing carbon black by a grafting technique and the electrothermal filament containing carbon black.

2. Description of Related Art

Since so many improvements have taken place in the textile field, cloth has to have more features to attract consumers. Multiple features such as waterproofing or heat retention are added to finished cloth. How to make cloth retain heat is a special and valuable feature to textile manufacturers.
Numerous electrically conductive fibers with unstable electrical properties have been developed. Most of them are cloth combined with conductive media such as conductive filaments, conductive plates or semi-conductive membranes. However, the resultant cloth incorporating a conductive media is very heavy and inflexible so that the cloth is inconvenient to carry and handle and is hard to tailor to a desired shape. Although the cloth with conductive membrane has better resilient than other cloth with other conductive media, the cloth with conductive membrane still do not have water-proof efficiency and easily deteriorates after laundering and no longer conducts electricity. Other electrically conductive fibers are made by plating a metal layer on the surface of a non-conductive fiber or by formation of an electrically conductive coating layer on a fiber from resin or rubber in which electrically-conductive carbon black is incorporated. Drawbacks are their complex and difficult production processes or their easy loss of electrical conductivity during clearing involving chemical treatment and in actual use involving wear and repeated washing.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional electrically conductive fiber.
The main objective of the present invention is to provide a method of producing electrothermal filament containing carbon black that produces electrically conductive filaments having excellent resilience and durable electrical conductivity even after repeated laundering.
Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.

IN THE DRAWINGS

Fig. 1 is a block diagram of a method of producing electrothermal filaments containing carbon black in accordance with the present invention;
Fig. 2 is a schematic diagram of the method in Fig. 1 being carried out; and
Fig. 3 is a cross-sectional side plan view of an electrothermal filament containing carbon black in accordance with the present invention.
With reference to Fig. 1, a method of producing an electrothermal filament containing carbon black in accordance with the present invention comprising the acts of obtaining the materials, grafting carbon black to monomers to form grafted copolymers, coating a filament with the grafted copolymers, laminating a membrane on the filament and attaching two electrodes to each electrothermal filament.
The material that must be obtained to perform the method of producing an electrothermal filament containing carbon black consists of micro-powder carbon black, a grafting monomer, an initiator, a terminating agent, nitrogen gas and rolls of a membrane. Carbon black is micro-particles and is conductive material. The grafting monomer is styrene, and the initiator contains 0.5~2% benzoyl peroxide. The terminating agent is acetone. The membrane is a soft, flexible material such as a polyethylene (PE) or thermoplastic urethane (TPU) elastomer.
To graft the carbon black to a monomer, the carbon black is mixed with a grafting monomer and an initiator. Carbon black and styrene are respectively 8~15% and 80~90% with the residual proportion being the initiator. At the end of the grafting step, the terminating agent is added to the mixture of carbon black and the monomer to stop the grafting reaction.
The carbon black, grafting monomer (styrene) and the initiator (benzoyl peroxide) are mixed in a reaction tank to form a grafted copolymer. Then, nitrogen gas is guided into the reaction tank to maintain the temperature of mixture in the tank at 60°C. The grafting reaction takes 6~8 hours. At the end of the grafting reaction, the terminating agent (acetone) is added to the reaction tank to stop the grafting reaction thereby controlling the quantity of carbon black in the grafted copolymer. Consequently, the quality of the grafted copolymer is controlled and stable. The grafting reaction is depicted in the following chemical reaction: Carbon black + C₆H₅-(C₂H₂) 60°C for 6~8hr carbon black-(C₂H₂)-C₆H₅
According to this reaction, the carbon black is grafted with monomer by free radicals of the carbon black to coat a layer of monomer around outer periphery of the carbon black micro-particles. Whereby, each carbon black micro-particle repulse others to avoid coagulation between carbon black micro-particles.
To coat filaments with grafted copolymer, filaments are passed through the grafted copolymer to coat the filaments with a layer containing carbon black. With reference to Fig. 2, the filament (10) wound on a spindle (101) is reeved around rollers (12) through grafted copolymer (20) in a first tank (11). When the filament (10) passes through the grafted copolymer (20) in the first soaking tank (11), the grafted copolymer (20) permeates and coats the filament (10). After the filament (10) leaves the grafted copolymer (20) in the first tank (11), a pair of rollers (12) squeegees excess grafted copolymer (20) from the filament (10). Then the filament (10) is passed through grafted copolymer (20) in a second tank (13) and a third tank (15) to increase the thickness of the grafted copolymer on the filament (10) to ensure that sufficient the carbon black is on the filament (10). After coating the filament (10) with the grafted copolymer (20), the filament (10) is delivered to a curing roller assembly (17) to completely cure the grafted copolymer on the filament (10).
After curing the grafted copolymer on the filament, two sheets of a membrane (25) are respectively delivered from two membrane spindles (18) respectively mounted on opposite sides of the filament (10). The membranes (25) are laminated on the filament (10) by a pair of compressing wheels (181). The membrane (25) on the filament (10) keeps the carbon black from easily coming off the filament (10) and provides an insulating layer to complete the electrothermal filament. Lastly, the electrothermal filaments are winded up on a final roller (19).
With reference to Fig. 3, each electrothermal filament (30) is composed of a conductive core (21) of grafted copolymer and a membrane (25) surrounding around the core (21). The conductive core (21) has two ends projecting out of the membrane (25), and two electrodes (35) are respectively attached to opposite ends of the conductive core (21). The electrothermal filament (30) generates heat when current passes through the conductive core (21).
Based on the foregoing description, the electrothermal filament containing carbon black and the method of producing said filament have the following advantages:
1. Because the carbon black is grafted with grafting monomer, the carbon black has polarization to cause repulsion effect after grafting with the monomer and then is evenly distributed when coated on the filament. Therefore, the electrothermal filament uses less carbon black but has excellent conductivity to evenly heat the electrothermal filament.
2. The soft and flexible membrane coating around the conductive core encloses the carbon black inside to prevent the carbon black from separating from the filament during washing. Additionally, the flexibility of the electrothermal filament is improved after laminating the membrane.
3. The electrothermal filament using carbon black to form the conductive core is light and efficiently generates heat. Therefore, the cloth made of the electrothermal filament is light-weight and has excellent warming features during use.
Although the invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.

Claims

A method of producing electrothermal filament containing carbon black, the method comprising following acts:

obtaining carbon black, a grafting monomer, an initiator, a terminating agent, nitrogen gas and rolls of a membrane;

grafting the carbon black with monomers by mixing the carbon black with the grafting monomer and initiator to graft the carbon black to the monomer to form grafted copolymers and then adding a terminating agent to the mixture to stop the grafting;

coating the filaments with the grafted copolymers by passing the filaments through the grafted copolymers to apply a layer of carbon black on the filaments; and

laminating membranes on the filament.
The method of producing electrothermal filament containing carbon black as claimed in claim 1, wherein
the monomer is styrene;
the initiatior is a 0.5~2% benzoyl peroxide solution;
the terminating agent is acetone;
the membranes are soft and flexible material selected from the group comprising polyethylene (PE) or thermoplastic urethane (TPU) elastomer; and
the carbon black proportion is 8~15%;
the styrene monomer is 80~90%; and
the remaining component is benzoyl peroxide solution.
The method of producing electrothermal filament containing carbon black as claimed in claim 2, wherein the carbon black, styrene monomer, and benzoyl peroxide are mixed to form a grafted copolymer;
wherein nitrogen gas is added to maintain a temperature of 60°F for 6 to 8 hours.
The method of producing electrothermal filament containing carbon black as claimed in claim 1, where the act of coating the filaments with the grafted copolymer comprises passing the filament through the grafted copolymer three times to ensure sufficient carbon black is on the filament.
The method of producing electrothermal filament containing carbon black as claimed in claim 1 further comprising the act of respectively attaching two electrodes to opposite ends of each electrothermal filament.
An electrothermal filament in accordance with the present invention comprising:

grafted copolymer formed by grafting carbon black to a monomer;

a filament having two ends coated with the grafted copolymer; and

a membrane laminated on the filament having the grafted copolymer as insulation.
The electrothermal filament as claimed in claim 6, wherein the electrothermal filament further has two electrodes respectively attached to opposite ends of the electrothermal filament.