Patent Application
20140255651
This disclosure is directed to a weatherstrip, and more particularly to a glassrun weatherstrip that operatively engages perimeter edge portions of a movable vehicle window. However, the disclosure may find application in related environments and applications encountering the same types of issues and end use requirements.
One end result of a glassrun weatherstrip focuses on producing a very rigid vulcanized rubber compound that provides structural support for automotive weatherstrips. High durometer, dense, formulations developed for glassrun weatherstrips are typically achieved by using, for example, highly crystalline EPDM polymers and/or addition of hardening agents like phenolic novolac resin and organic amines like Hexa-80 (hexamethylenetetramine).
Existing plasticizers incorporated into high hardness rubber formulations used in connection with the manufacture of glass run weatherstrips typically include paraffinic or napthenic oil. However, there are supply constraints associated with paraffinic oil. Being a petroleum-based oil leads to fluctuations in both supply and cost. Thus, control over both the supply and cost would be advantageous, and any ability to reduce the amount of petroleum-based oil in the final product is desirable.
There is always a desire to improve the performance of the glassrun weatherstrip, for example, increased hardness, lower cost, renewable resource, etc. However, material properties of the cured weatherstrip can suffer when high crystalline EPDM polymer is used to raise the hardness level. The highly crystalline polymers unfortunately encounter issues with compression set, i.e., pressure applied to the surface of the weatherstrip body leaves an indent or impression in the body which can be permanent, and thereby prevents the weatherstrip from properly supporting and/or sealing in that region. Therefore, it would be desirable to develop a rubber formulation for such use that reduces or eliminates the use of one or more crystalline polymers.
In addition, other hardening agents can produce low levels of formaldehyde which is undesirable. Thus, other select hardening agents are avoided for such reasons.
Another option is to incorporate a metal carrier into the glassrun weatherstrip assembly. For example, it is common to use a rigid metal carrier such as aluminum or steel that provides desired strength and rigidity to the final weatherstrip. For example, the carrier may be lanced or formed in a manner that allows for ease of bending as the weatherstrip must be able to conform to a radius of curvature. Metal carriers though are undesirable in glassrun weatherstrips because of the increased weight that the metal carrier contributes to the vehicle. Increased weight is detrimental to fuel economy. Further, metal is generally more expensive than rubber so that eliminating the metal carrier and replacing it with rubber is desirable as long as the performance characteristics are not substantially adversely impacted.
Thus, a need exists for a rubber formulation that still provides the desired performance characteristics, including high hardness, and yet is made at least in part from a renewable resource.
A weatherstrip configured for engagement with an associated vehicle window is provided that is at least partly formed from a renewable (“green”) oil, preferably soybean oil that has been completely hydrogenated.
A body of the weatherstrip includes regions having a high hardness. The high hardness regions including soybean oil as an ingredient in the body. Flexible seal portions extend outwardly from the body and are adapted for sliding engagement with the associated vehicle window.
The soybean oil is preferably approximately 1-25 weight % of a material forming the body.
The material forming the body is a rubber formulation, that typically includes an EPDM polymer.
The body has a Shore A durometer on the order of 80-95.
The body is free of a carrier.
A method of forming a weatherstrip exhibiting high hardness is disclosed herein.
The method includes providing a rubber formulation, and substituting at least a portion of a plasticizer with fully hydrogenated soybean oil.
The substituting step includes melting the fully hydrogenated soybean oil, and mixing the liquid fully hydrogenated soybean oil into the rubber formulation at the same time in a mixer.
The fully hydrogenated soybean oil is substituted at a rate of approximately 1-25% weight of the total weight in the method.
The method further includes curing the rubber formulation containing the fully hydrogenated soybean oil, and the cured weatherstrip having a Shore A durometer on the order of 80-95.
Preferably the mixing of the liquid fully hydrogenated soybean oil into the rubber formulation occurs at a temperature around 150 degrees F. or greater, for example, the mixing in one preferred arrangement occurring at temperatures ranging from about 250 degrees F. to approximately 320 degrees F.
The method includes at least one of eliminating a carrier from the weatherstrip, omitting or reducing highly crystalline polymers from the mixture, and omitting or reducing hardening agents from the mixture.
One benefit is associated with the high durometer of the resulting weatherstrip.
Another advantage resides in the light weight of the weatherstrip.
Still another benefit is the ability to incorporate a renewable resource in the elastomeric material that forms at least a portion of the weatherstrip.
Yet another advantage is associated with the improved fuel economy that results from eliminating the use of a metal carrier in the weatherstrip.
Still other benefits and advantages will become apparent upon reading and understanding the following detailed description.
A lower edge of the window opening as defined by the door is often referred to as a beltline 120. Extending along the beltline 120 is a beltline weatherstrip portion or beltline portion of the weatherstrip module identified as 122. A cross-sectional view of the beltline weatherstrip 122 is shown in
Illustrated in
Although not specifically illustrated or described, other configurations of the weatherstrip and particularly a glassrun weatherstrip (e.g., portions along the header or pillar) may have different conformations but still require hardened regions that abut with perimeter edges of the movable window so that the teachings of the present disclosure are fully applicable.
One important distinction is that the soybean oil is preferably fully hydrogenated. For purposes of this disclosure, “fully hydrogenated” means at least greater than 95% hydrogenated (since testing demonstrated that 95% hydrogenation did not provide acceptable results) and up to and including 100% hydrogenation, and partially hydrogenated means 95% and below. As is well-known, hydrogenation is a chemical reaction of treating a compound with hydrogen (H2) which results in a reduced or saturated organic compound. Typically, pairs of hydrogen atoms are added as a result of the process. This changes the physical state of the soybean oil from a liquid to a solid. Thus when the fully hydrogenated soybean oil is added to the rubber formulation, it is necessary to heat the formulation above the melting point (150° F.).
As illustrated in
Further, the performance of the resultant compounds was also measured over a range of temperatures from approximately 50 to 275° C. As graphically illustrated in
As previously noted, the fully hydrogenated soybean oil is solid at room temperature. However when heated, it becomes liquid, i.e., the fully hydrogenated soybean oil has a heat flow as graphically evidenced in
The present disclosure allows substantially similar performance characteristics to be achieved by using fully hydrogenated soybean oil to raise hardness without the use of highly crystalline the EPDM polymers, hardening agents, or metal carrier. The end result is a high durometer, lightweight glass run weatherstrip with improved material properties to help meet the demands for improved fuel economy and utilization of renewable resources.
Since soybean oil is liquid at room temperature, it can be hydrogenated to remove unsaturation. The hydrogenation process converts the oil from a liquid to a solid at room temperature; however, fully hydrogenated soybean oil begins to melt around 150° F. so it is easily incorporated into the rubber matrix during mixing. Fully hydrogenated soybean oil is required for this disclosure to prevent unsaturation in the soybean oil from interfering with cross-linking when vulcanizing the rubber. The soybean oil solidifies to raise hardness once the vulcanized weatherstrip is cooled to temperatures below 150° F.
This disclosure uses the fully hydrogenated soybean oil to raise hardness without the use of highly crystalline the EPDM polymers, hardening agents, or metal carrier, which features can be either reduced or omitted entirely. As is evident from the test samples, the level of hardness can be adjusted by simply increasing or reducing the ratio of petroleum-based oil to hydrogenated soybean oil in the EPDM weatherstrip formulation. For example, a lower petroleum-based oil to soybean oil ratio will raise the durometer/hardness of the EPDM rubber compound hence increasing the stiffness of the glassrun weatherstrip. The end result is a high durometer, lightweight weatherstrip with improved material properties.
This written description uses examples to describe the disclosure, including the best mode, and also to enable any person skilled in the art to make and use the disclosure. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
