Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-09-11
2002-05-07
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06384116
ABSTRACT:
This invention relates to a urea formaldehyde (UF) resin modified with a water soluble non-ionic amine oxide. The modified resin has utility for increasing the tear strength of products prepared from glass fiber mats treated with the modified UF resin. This invention also relates to the further modification of the UF resin containing the amine oxide wherein such further modification includes the addition thereto of an anionic acrylic latex and/or a water soluble polymer of a polymerized ethylenically unsaturated carboxylic acid monomer whereby the tear property of the treated mat is significantly increased while maintaining the high level of tensile strength. The water soluble polymer comprises 40% to 100% by weight, based on polymer weight, of a polymerized ethylenically unsaturated carboxylic acid monomer wherein the polymer has a weight average molecular weight of from 100,000 to 2,000,000 and is also referred to herein simply as the water soluble polymer. The invention further relates to glass fiber mats impregnated with the modified UF resins, as well as roofing products and backing sheets for vinyl flooring utilizing the modified urea formaldehyde impregnated glass fiber mats. This invention also relates to a process for choosing the most desirable combination of binder and mat for manufacture of binder treated glass fiber mats.
BACKGROUND AND PRIOR ART
Asphalt coated glass fiber mats are increasingly used as roofing shingles, replacing similar sheets traditionally made of wood or cellulose fibers. This type of glass fiber based roofing product has advantages such as in strength properties and in fire retardant characteristics.
Glass fiber mats are usually made by a wet-laid non-woven process somewhat similar to the paper making process. Examples of such processes can be found in U.S. Pat. Nos. 2,906,660; 3,766,003 and 3,838,995, each of which is incorporated herein by reference in its entirety. The wet-laid non-woven process for glass fiber mats can be described in the following stages:
The first stage involves forming an aqueous suspension of short length fibers under agitation in a mixing tank which is sometimes called the “pulper”. Glass fibers used in this application are generally about 0.5 to about 2 inches in length with typical diameters of about 3 to 20 microns. The glass fibers are also “sized”. Sizing is a process in which glass fiber manufacturing companies use proprietary chemistry and processes to provide various functions to the surface of the fiber. The functions are:
(A) As lubricants-coolants in the glass forming process while passing through the chopper to keep it dense;
(B) As moisture binding agents; and
(C) As aids to dispersion in the pulper.
The sizing process and sizing agents are also used to affect the physical properties of the glass fiber mats.
The short glass fibers come as strands or bundles and do not disperse well when mixed with water. In fact, upon prolonged agitation, the glass fibers agglomerate as large clumps which are difficult to re-disperse. Dispersion aids, usually surface active products, are used to facilitate the dispersion. High molecular weight polymers such as polacrylamide and hydroxyethyl cellulose are used to increase the viscosity of the media (water) in the pulper to help the suspension of the glass fibers. The dispersion of these glass fibers is critical for the formation of the mat.
The second stage of the process involves the formation of a glass fiber mat. The glass fiber dispersion in the “pulper” is further diluted with water, and passed through a mat forming machine. The fibers are collected on a moving wire screen in the form of a non-woven mat. Water is removed by gravity and, more often, by vacuum devices in the forming machine. The forming machine often moves at a speed of several hundred feet per minute. At the end of the second stage, the mat of glass fibers maintains its physical integrity and although it still contains water, there is little or no drippage of water from the mat.
During the process of mat forming, the wet mats need to be transferred from one section of the machine to another. Therefore, it is important that the mat has enough wet web strength to maintain its integrity during the non-woven wet laid process.
The third stage of this process involves binder application. Binders are applied to the moving mat by, for example, a falling film or curtain coater. After the binder application, the treated mats go through a de-watering device, which removes excess water to ensure a thorough application of binder throughout the glass fiber mat.
The fourth stage of the process involves the drying and curing of the glass fiber mats treated with binder. The treated mats are then passed through a series of ovens or other heating devices, usually at a temperature range of 200 to 250° C. The binder treated mats are dried and the binder is cured when the mat passes through the ovens. The degree of curing or cross-linking of the thermosetting urea formaldehyde resin, along with its modifiers such as amine oxide, latex and/or water soluble polymers, affects the strength properties of the glass fiber mat. The interaction between the glass fiber surface and the binders during curing affects the distribution of the binder network and the glass fibers and therefore is important in determining the physical properties of the finished mats.
After the glass fiber mat has been formed and cured, it can be passed through a process which involves coating the mat with hot asphalt to form a roofing product such as roofing shingles. While the strength of the roofing product depends primarily on the strength of the mat, the tear property sometimes does not transfer fully to the roofing product.
Roofing products need to meet governmental and industrial strength requirements. The industry has successfully met the requirements in the past and has been able to optimize the tensile and tear properties. Recently, however, the need to withstand severe weather conditions caused a demand for further improvement in the tear property of the roofing shingles.
It is generally accepted that there is a balance between the tensile strength and the tear strength of the glass fiber mats. Processes in the prior art have provided an optimum balance between the tensile and tear properties which meet the earlier requirements. It is generally understood that the technical parameters in which the industry can work to obtain an increase in mat tensile also tends to lower tear strength. Therefore, it has been difficult to meet tear strength requirements without sacrificing the tensile strength. A simple solution to this problem is to increase the basis weight of the mat. However, this is a costly approach, and also provides an undesirable increase in the load of the shingles which the roof has to support.
Glass fiber producers have also tried to provide a solution by changing the sizing compositions and sizing technology. Recently these producers have developed fibers which provide high tear values or high tensile values to the glass fiber. These changes have not met the optimum requirement of the industry because of the following observations and reasons:
(1) The fiber either provides very high tensile strength and significant loss in tear strength or provides very high tear and substantial loss in tensile strength.
(2) The sizing chemistry has a significant effect on the distribution of the binder and fiber during curing. The effects of sizing changes can be so substantial that it makes it difficult to balance the desirable properties by sizing alone.
(3) A small amount of sizing material will dissolve into the white water during mixing and storage. This amount may be small, but when one looks at the very small amount of surfactant or dispersing agent used in the system, the amount of sizing material dissolved in the white water will significantly affect the white water chemistry and the dispersing of the fibers in the pulper.
Points (2) and (3) above are probably the reasons which make it difficult to optimize the tear and tensile strength by us
Chan Lock-Lim
Wallace Peter DeBaun
Borden Chemical, Inc.
Maskas George P.
Michl Paul R.
Van Wyck Kenneth P.
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