Patent Application
20160168502
This application is based on and claims the benefit of priority to Korean Patent Application No. 10-2014-0181772, filed on Dec. 16, 2014 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
The present invention relates to a composition for a brake fluid for a vehicle. The composition may decrease a moisture absorption amount of the brake fluid in the air and maintain a high boiling point of the brake fluid for a long period of time, such that a period for changing break fluid change may be extended and corrosion prevention performance and metal wear prevention performance may be improved. Particularly, the composition includes oil soluble polyalkylene glycol (OSP) at a predetermined content ratio with respect to a mixed solvent which comprises boric ester and alkylene glycol alkyl ether at a predetermined content ratio.
A brake fluid of a vehicle plays an important role of accurately transferring pressure generated in a master cylinder to a wheel cylinder. When a problem occurs in this process, brake responsibility may be deteriorated. Indeed, the brake fluid as described above may require several essential factors associated with chemical and physical properties thereof. Among them, a high equilibrium reflux boiling point (ERBP) may be a primary essential factor. For example, the brake fluid itself is a liquid that may not boil or evaporate at normal condition, but since a high temperature or heat is generated during a braking operation, the brake fluid may boil depending on the situation. If the brake fluid boils, the pressure of the master cylinder may not be accurately transferred, such that stable braking force may not be applied. Further, a temperature of frictional heat generated at the time of frequently using a disk brake in a brake system is about 800° C., and brake fluid may be oxidized by the heat, thereby causing safety problems and deteriorating corrosion prevention performance.
Further, a high wet equilibrium reflux boiling point may be another essential factor. The brake fluid as being a liquid may require a low hygroscopic property, however, it is also important that a boiling point is not decreased even though the brake fluid absorbs substantial moisture. For instance, when the boiling point is decreased due to moisture absorption of the brake fluid in the air, a vapor lock phenomenon may be generated, thereby causing a safety accident.
In addition, a viscosity change rate of the brake fluid should not vary substantially in a wide temperature range. Further, a metal corrosion inhibitor, an oxidation stabilizer, and the like, may be added to the brake fluid in order to prevent corrosion of various metals present in a brake device to allow the brake device to have durability.
As generally used brake fluid for vehicles, DOT-3 brake fluid including a glycol ether compound as a sole solvent, and DOT-4 brake fluid including about 30 to 60 wt % of a boric ester compound have been mainly used. Since the DOT-3 brake fluid includes only the glycol ether compound having a low molecular weight, the brake fluid may absorb moisture in the air at the time of being used for a long period of time to cause a vapor lock phenomenon while decreasing a wet boiling point, thereby generating an accident due to brake inability, and long-term metal corrosion prevention performance may be deteriorated. Further, since at least DOT-4 brake fluid includes the boric ester compound, an equivalent reflux boiling point and a wet boiling point may be elevated, such that safety may be improved as compared to the DOT-3 brake fluid. However, when moisture contacts with the brake fluid, the boric ester compound therein may be hydrolyzed and boric acid may be precipitated, which deteriorates physical properties as the brake fluid and generates foreign materials. As such, in order to prevent boric acid from being precipitated, an amine or silane based stabilizer may be added thereto and then used. Accordingly, a novel composition which can prevent moisture absorption of brake fluid and prevent a decrease in a wet boiling point due to moisture absorption has been still in demand.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.
In preferred aspect, the present invention provides a composition for a brake fluid of a vehicle. The composition may decrease a moisture absorption amount of the break fluid in the air and maintain a high boiling point thereof during a long period of time, thereby securing a smooth operation of a master cylinder, extending brake fluid change period and improving corrosion prevention performance and metal wear prevention performance.
The present inventors have studied in order to solve the above-mentioned problems according to the related art, and as a result, the present inventors have found that when oil soluble polyalkylene glycol (OSP) is mixed with a DOT-4 brake fluid in the related art, an moisture absorption amount of brake fluid in the air was decreased as compared to a conventional brake fluid.
According to an exemplary embodiment of the present invention, a composition for brake fluid of a vehicle may comprise an amount of about 30 to 60 wt % of a boric ester compound; an amount of about 30 to 60 wt % of alkylene glycol alkyl ether; and an amount of about 0.05 to 10 wt % of oil soluble polyalkylene glycol (OSP), all the weight % (wt %) based on the total weight of the composition.
The oil soluble polyalkylene glycol (OSP) may be a polymer, and particularly, the polymer may include a repeating structure represented by the following Chemical Formula 1.
In Chemical Formula I, R1 and R2 , may be same or different, and each is independently a linear or cyclic alkyl group having at least two carbon atoms; and m and n are each independently an integer of 10 or greater.
The alkylene glycol alkyl ether may be at least one selected from the group consisting of triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, polyethylene glycol monomethyl ether, polyethylene glycol monobutyl ether, and diethylene glycol monobutyl ether.
The composition for the brake fluid may further comprise an amount of about 0.1 to 2.0 parts by weight of a metal corrosion inhibitor and an amount of about 0.1 to 2.0 parts by weight of an antioxidant, based on 100 parts by weight of the composition of brake fluid. Preferably, the metal corrosion inhibitor may include an amount of about 0.05 to 1.5 parts by weight of an alkylamine based metal corrosion inhibitor and an amount of about 0.05 to 0.5 parts by weight of a triazole based metal corrosion inhibitor, based on 100 parts by weight of the composition of brake fluid. In particular, the alkylamine based metal corrosion inhibitor may be at least one selected from the group consisting of methylamine, dibutylamine, triethylamine, triethanolamine, and cyclohexylamine, and the triazole based metal corrosion inhibitor may be at least one selected from the group consisting of benzotriazole, mercaptobenzotriazole, and tolyltriazole.
Preferably, the antioxidant may be 3,5-di(tert-butyl)-4-hydroxytoluene (BHT).
Further provided are vehicles that comprise the composition as described herein. In particular, the composition may be used as a brake fluid in the vehicles.
Other aspects of the invention are disclosed infra.
The above and other objects, features and advantages of the present disclosure will be more apparent from the following detailed description taken in conjunction with the accompanying drawings.
It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.”
The present invention relates to a composition of a brake fluid which may decrease a moisture absorption amount of brake fluid in the air, decrease metal friction, and have improved corrosion prevention performance.
In an exemplary composition for the brake fluid according to the present invention, a mixed solvent in which boric ester and alkylene glycol alkyl ether are mixed at a predetermined content ratio may be used, and OSP may be included therein at a predetermined content ratio. Additionally, the composition for brake fluid may further contain a metal corrosion inhibitor or an antioxidant.
Each of the ingredients of the composition for brake fluid according to various exemplary embodiment of the present invention will be described below in detail.
The composition for brake fluid may include the mixed solvent which is prepared by mixing boric ester and alkylene glycol alkyl ether at a predetermined content ratio. That is, based on the total weight (100%) of the composition for brake fluid, an amount of about 30 to 60 wt % of boric ester and an amount of about 30 to 60 wt % of alkylene glycol alkyl ether can be mixed.
Boric ester contained in the mixed solvent may be used in order to prevent a boiling point from being decreased by moisture absorption, and boric ester may be included in a content range of about 30 to 60 wt % based on the total weight (100%) of the composition for brake fluid. When the boric ester is included in less than the above-mentioned range, sufficient desired effect may not be obtained, and when the boric ester is included in greater than the above-mentioned range, manufacturing cost may be increased, and boric acid may be precipitated.
The alkylene glycol alkyl ether included in the mixed solvent may be used in order to have a lubrication operation in a cylinder and a piston in a brake system to be smoothly performed. Examples of the alkylene glycol alkyl ether may be, but not limited to, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, polyethylene glycol monomethyl ether, polyethylene glycol monobutyl ether, diethylene glycol monobutyl ether, and the like. Preferably, the alkylene glycol alkyl ether may be included in a content range of about 30 to 60 wt % based on the total weight (100%) of the composition for brake fluid.
Further, the composition for brake fluid may comprise OSP in addition to the mixed solvent, and may further contain the metal corrosion inhibitor or the antioxidant.
The oil soluble polyalkylene glycol (OSP) may be used in order to decrease the moisture absorption amount of the brake fluid in the air and maintain the high boiling point of the brake fluid for a long period of time. As such, the OSP may be an essential ingredient used to extend brake fluid change period and improve corrosion prevention performance and metal wear prevention performance. In particular, the OSP may be a polymer having a repeating structure represented by the following Chemical Formula 1.
In Chemical Formula I, R1 and R2 are same or different, and each is independently a linear or cyclic alkyl group having at least two carbon atoms; and m and n are each independently an integer of 10 or greater.
The OSP may be included in the composition in a content range of about 0.05 to 10 wt % based on the total weight (100%) of the composition for brake fluid. When the content of OSP is substantially less than the above-described content, sufficient effect of decreasing the moisture absorption amount may not be obtained. When the content is substantially greater than the above described content, since OSP has a property of significantly swelling styrene-butadiene rubber (SBR) or ethylene-propylene diene monomer (EPDM) rubber, this rubber may be excessively swelled, such that a volume of EPDM in the master cylinder may be significantly increased, thereby hindering a piston operation. When the DOT-4 brake fluid is prepared, OPS may be used in a content range of about 0.05% to 10% in a brake fluid in order to have an EPDM rubber cup of the master cylinder in the brake system to smoothly perform a piston operation. It was confirmed that when an amount of about 0.05 to 10% of OSP, e.g. a polyalkylene glycol group, is added, the moisture absorption amount of the brake fluid in the air was significantly different as compared to the case of adding a general polyalkylene glycol in addition to lubrication performance which is a basic function of the polyalkylene glycol. Further, when the OSP is added in greater amount than the above-described content, OSP may hinder the piston operation as described above.
Since pipes made of metal materials such as the master cylinder, a wheel cylinder, and the like, may be corroded by boric ester and alkylene glycol alkyl ether in the mixed solvent, the metal corrosion inhibitor may be suitably used in order to prevent corrosion as described above. Preferably, a mixture of an alkylamine based and triazole based metal corrosion inhibitors may be used. Particularly, the alkylamine based metal corrosion inhibitor, which is an amine compound substituted with 1 to 3 linear, branched, or cyclic alkyl groups having 1 to 10 carbon atoms, may be, but not limited to, at least one selected from the group consisting of methylamine, dibutylamine, triethylamine, triethanolamine, and cyclohexylamine. The triazole based metal corrosion inhibitor may be, but not limited to, at least one selected from the group consisting of benzotriazole, mercaptobenzotriazole, and tolyltriazole.
The metal corrosion inhibitor may be included in a content range of about 0.1 to 2.0 parts by weight based on 100 parts by weight of the composition for brake fluid. When the content of the metal corrosion inhibitor is substantially less than the above described content, sufficient effect of preventing corrosion may not be obtained, and when the content thereof is substantially greater than the above described content, loud noise may be generated at the time of operating the master cylinder in the brake system. Preferably, the metal corrosion inhibitor may be a mixture of the alkylamine based metal corrosion inhibitor in an amount of about 0.05 to 1.5 parts by weight and the triazole based metal corrosion inhibitor as the metal corrosion inhibitor in an amount of about 0.05 to 0.5 parts by weight, all the weight parts based on 100 parts by weight of the composition for brake fluid.
The antioxidant may be included in the composition to prevent oxidation, and the antioxidant may be at least one selected from general antioxidants used in the related art. Preferably, the antioxidant may be, but not limited to, 3,5-di(tert-butyl)-4-hydroxytoluene (BHT).
The antioxidant may be included in a content range of about 0.1 to 2.0 parts by weight based on 100 parts by weight of the composition for brake fluid. When the content of the antioxidant is substantially less than the above-described content thereof, sufficient effect of preventing oxidation may not be obtained, and when the content thereof is substantially greater than the above-described content thereof, loud noise may be generated at the time of operating the master cylinder in the brake system.
According to various exemplary embodiments of OSP-containing compositions for brake fluid, the high boiling point of the brake fluid may be maintained for a long period of time, and an effect as an extreme pressure agent may be excellent, such that wear of surfaces of iron balls may be decreased, and metal corrosion prevention performance may be improved.
The present invention as described above will be described in detail based on the following Example and Experimental Example, but the present disclosure is not limited thereto.
Compositions for brake fluid based on DOT-4 were prepared using ingredients to have content ratios as illustrated in the following Table 1.
Compositions for brake fluid in which OSP was added to a composition for DOT-4 brake fluid used according to the related art while changing a content of the OSP are illustrated in Table 1. In order to increase the content of OSP, contents of polyethylene glycol monobutyl ether, triethylene glycol monomethyl ether, and the boric ester compound in the mixed solvent were decreased as in Table 1, respectively, and a sum of the decreased content and an increased content of OSP were the same each other. Further, comparative Examples 1 and 2 are compositions for DOT-4 brake fluid according to the related art to which OSP was not added, such that Comparative Example 1 was a composition not containing polyalkylene glycol and Comparative Example 2 was a composition containing 10% of polyalkylene glycol. In the composition of Comparative Example 2, a content of the mixed solvent was decreased as compared to Comparative Example 1 so as to correspond to the content of added polyalkylene glycol. An example of OSP-containing compositions for brake fluid according to the present invention includes the compositions of Examples 1 to 6 illustrated in Table 1, and the compositions of Examples 1 to 6 and Comparative Examples 1 and 2 were confirmed through various Experimental Examples described below.
After 100 ml of each of the compositions for brake fluid based on DOT-4 (Examples 1 to 6 and Comparative Examples 1 and 2) of Table 1 was put into a beaker, the compositions were kept at room temperature for 15 days and moisture absorption amounts thereof in the air were compared and observed, as illustrated in Table 2. A brake fluid before the test was referred to as a novel solution, and the moisture absorption amount was measured every day for 15 days during the test, and the results were illustrated in Table 2.
A boiling point of the compositions before testing as Experimental Example 1 and a boiling point of the brake fluid after 15 days were compared with each other. The following Table 3 is a table illustrating comparison results of the boiling points of composition for brake fluid based on DOT-4 of Table 2.
As shown above, friction between metals may occur in an ABS/ESP module among brake system components at the time of performing a braking operation during driving a vehicle, and at the time of frequently performing the braking operation, wear prevention performance may be deteriorated due to metal friction, such that a brake distance may be increased at the time of performing the brake operation. As an extreme pressure/wear prevention test against metal friction of the prepared compositions for brake fluid based on DOT-4 (Examples 1 to 6 and Comparative Examples 1 and 2), a four ball wear prevention test according to ASTM D 4172 standard was performed.
Appearance of each of the compositions for brake fluid of Table 4 was illustrated in
It may be appreciated from the Experimental Examples 1 to 4 that when the OSP-containing composition for brake fluid was used according to an exemplary embodiment of the present invention, the moisture absorption amount (after keeping the brake fluids in the air for 15 days) was decreased by 0.7% to 7.1% as compared to DOT-4 brake fluids (Comparative Examples 1 and 2) according to the related art. In addition, the boiling point thereof was highly maintained by 8° C. to 32° C., and as results of the wear prevention test, iron balls were less worn. Further, as results of the appearance test, in the case of the OSP-containing composition for brake fluid according to an exemplary embodiment of the present invention, the color was not changed into reddish brown or black.
Considering all experimental results, the OSP-containing composition for brake fluid according to various exemplary embodiment of the present invention may provide substantially improved results in all of the Experimental Examples.
However, according to additional study results of the present inventors, in Examples 5 and 6 in which the content of the OSP was included greater than about 10 wt %, since the OSP has a property of significantly swelling styrene-butadiene rubber (SBR) or ethylene-propylene diene monomer (EPDM) rubber, the OSP may act as a factor of hindering a smooth piston operation of an EPDM rubber cup of a master cylinder. As such, although the OSP provides excellent moisture absorption prevention performance, high boiling point maintenance performance, and wear prevention performance as being included in the composition, the excessive content thereof was not suitable for the brake fluid.
The composition for brake fluid according to various exemplary embodiments of the present invention may decrease the moisture absorption amount in the air, and have the high boiling point of the brake fluid to be maintained for a long period of time, thereby extending the period for a brake fluid change as compared to the conventional brake fluid which does not include the OSP. Further, the composition for brake fluid according to various exemplary embodiments of the present invention may decrease metal friction and prevent metal corrosion, and thus the master cylinder of the vehicle may smoothly operate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2014-0181772 | Dec 2014 | KR | national |
