Process for the treatment of a fiber

Details Process for the treatment of a fiber Process for the treatment of a fiber

2001-06-15

2003-11-18

Padgett, Marianne (Department: 1762)

Coating processes

Direct application of electrical, magnetic, wave, or...

Electromagnetic or particulate radiation utilized

C427S553000

Reexamination Certificate

active

06649225

ABSTRACT:

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
None
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a process for treating moving fibers using high intensity ultraviolet light between 160 and 500 nm without higher wavelengths and ozone. The treatment enhances the strength of the fiber and bondability of the fiber is improved by increasing the oxygen in contact with the surface of the fiber.
(2) Description of the Related Art
In general, manufactured surfaces of substrates, such as the adhereneds in adhesive joints or reinforcing fibers in composites, usually contain undesirable compounds or additives that limit or reduce adhesion to an adhesive or paint film. Hence, surface preparation, which includes cleaning and activation of the surfaces, of polymeric, polymer composite, fibers or metal substrates is carried out prior to applying protective paint films or adhesive bonding. Surface preparation determines the mechanical and durability characteristics of the composite created. Currently, the techniques used for surface preparation are mechanical surface treatments (e.g. abrasion), solvent wash and chemical modification techniques like corona, plasma, flame treatment and acid etching. Each of the existing processes have shortcomings and thus, they are of limited use. Abrasion techniques create dust and abrasive wear waste, are found to be time consuming, labor intensive and have the potential to damage the adherent surface. Use of organic solvents results in volatile organic chemical (VOC) emissions. Wet chemical techniques (such as acid etching) are costly, create waste that must be disposed of or recycled and need tight control. Dry chemical methods (such as plasma etching) are usually batch processes and of limited use with regard to treating three dimensional parts.
The use of lasers for surface treatment is known in the art. The focused beams of the lasers make it difficult to treat a large surface or non-regular surfaces such as fiber tows containing thousands of fibers. U.S. Pat. No. 4,803,021 to Werth et al describes such a method. U.S. Pat. No. 4,756,765 to Woodroffe describes paint removal with surface treatment using a laser.
Plasma treatment of surfaces is known in the art. Relatively expensive equipment is necessary for such treatments and plasmas are difficult to control. The surfaces are treated with vaporized water in the plasma. Illustrative of this art are U.S. Pat. Nos. 4,717,516 to Isaka et al., 5,019,210 to Chou et al., and 5,357,005 to Buchwalter et al.
A light based process which cleans a substrate surface also creates a beneficial chemistry on the surface for adhesive bonding and paintability is described in U.S. Pat. No. 5,512,123 to Cates et al. The process involves exposing the desired substrate surface to be treated to flashlamp radiation having a wavelength of 160 to 5000 nanometers. Ozone is used with the light to increase the wettability of the surface of the substrate being treated. Surfaces of substrates such as metals, polymers, polymer composites are cleaned by exposure to the flashlamp radiation. The problem with the Cates et al process is that the surface of the substrate is heated to a relatively high temperature, particularly by radiation above 500 nanometers and relatively long treatment times. Related patents to Cates et al are U.S. Pat. Nos. 3,890,176 to Bolon, 4,810,434 to Caines; 4,867,796 to Asmus et al; 5,281,798 to Hamm et al and 5,500,459 to Hagemever et al and U.K. Patent No. 723,631 to British Cellophane. Non-patent references are: Bolon et al., “Ultraviolet Depolymerization of Photoresist Polymers”, Polymer Engineering and Science, Vol. 12 pages 109 to 111 (1972). M. J. Walzak et al., “UV and Ozone Treatment of Polypropylene and poly(ethylene terephthalate)”, In: Polymer Surface Modification: Relevance to Adhesion, K. L. Mittal (Editor), 253 to 272 (1995); M. Strobel et al., “A Comparison of gas-phase methods of modifying polymer surfaces”, Journal of Adhesion Science and Technology, 365 to 383 (1995); N. Dontula et al., “A study of polymer surface modification using ultraviolet radiation”, Proceedings of 20th Annual Adhesion Society Meeting, Hilton Head, S.C. (1997); C. L. Weitzsacker et al., “Utilizing X-ray photoelectron spectroscopy to investigate modified polymer surfaces”, Proceedings of 20th Annual Adhesion Society Meeting, Hilton Head, S.C. (1997); N. Dontula et al., “Ultraviolet light as an adhesive bonding surface pretreatment for polymers and polymer composites”, Proceedings of ACCE'97, Detroit, Mich.; C. L. Weitzsacker et al., “Surface pretreatment of plastics and polymer composites using ultraviolet light”, Proceedings of ACT'97, Detroit, Mich.; N. Dontula et al., “Surface activation of polymers using ultraviolet activation”, Proceedings of Society of Plastics Engineers ANTEC'97, Toronto, Canada. Haack, L. P., et al., 22nd Adhesion Soc. Meeting (Feb. 22 to 24, 1999).
Non-pulsed, low intensity UV lamps have been used by the prior art. These are described in: “Experimental Methods in Photochemistry”, Chapter 7, pages 686 to 705 (1982). U.S. Pat. No. 5,098,618 to Zelez is illustrative of the use of these types of lamps. The UV light is preferably at 185 and 254 nm wavelengths in the presence of oxygen which generates atomic oxygen and ozone. The result is that the surfaces are more hydrophilic. The treatments are for 5 to 120 minutes which is a relatively long time. The lamps are low pressure and have an intensity of 10 to 15 m-Watts/cm
2
. The substrate is a distance of no more than 1.25 cm. The lamps are relatively low power and thus require a long treatment time.
There are multiple prior art processes for the surface treatment of carbon fibers. Carbon fibers are routinely used in aerospace, automotive, recreational, and durable goods markets. Three major methods are currently practiced: 1. Anodic oxidation, a wet process where the proper voltage and electrolyte solution concentration must be maintained; 2. Exposure to ozone gas at elevated temperature, where ozone concentration and temperature must be maintained; and 3. Treatment in caustic solutions such as nitric acid, where solution strength and treatment time must be maintained. Organic polymer fiber composites are experiencing 15% annual growth and a new method of fiber surface treatment could find applications in both fiber-thermoset and fiber-thermoplastic matrix composites.
U.S. Pat. No. 3,723,607 to Kalnin describes a process wherein carbon fibers are heated to 900 to 1400° C. in an inert atmosphere and then subsequently heated in ozone at 75° to 175° C. for a period of time of at least 30 seconds. The process is expensive because of the heating steps. The process provides oxygen on the surface of the fibers and improved composite strength.
U.S. Pat. No. 3,754,957 to Druin also shows the need for treating the surface of carbon fibers with oxygen. The fibers are heated at 1000° C. to 1800° C. in the presence of oxygen. The fibers form better composites.
U.S. Pat. No. 4,832,932 to Tada et al describes treating fibers to increase the oxygen content of the surface. Various methods are described including heating in ozone at 200° C. This patent also shows the need for providing oxygen in the surface part of the fibers.
Thus, there is a clear need to provide an oxygenated carbon fiber surface which provides for the preparation of improved composites. The problem is that the prior art processes require considerable amounts of energy, create waste products, require careful control and thus are expensive. There is a need for an improved process.
A disadvantage of the ultraviolet lamp fiber treatments of the prior art is that they are time consuming and sometimes unreliable. To achieve suitable surface chemistries for adhesive bonding and painting purposes, exposure times for certain materials like polypropylene, thermoplastic olefins (TPO's) tend to be of the order of 5 to 60 minutes. In many cases, there is a limit on the length of time to which one may expose the substrates to UV since

Affiliated with

Also associated with

Rating

Process for the treatment of a fiber does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for the treatment of a fiber, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the treatment of a fiber will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3164284