Bicycle chain lubricant composition

Abstract

Bicycle chain lubricant comprising base oil, a tackifier, and an anti-wear additive being either zinc dialkyl dithiophosphates (ZnDTP), molybdenum dithiocarbamates (MoDTC), or a mixture of both. The b

Description

Field of the Invention This invention relates to a bicycle chain lubricant composition and a method of lubricating a bicycle chain. Background of the invention Bicycles have chains that transfer power from the rotational movement of a cyclist to the wheels. These chains are classified as roller chains containing a series of pins, inner links which may be joined by bushings with cylindrical holes and outer plates, or a combination thereof. Roller chains require lubricants to reduce friction between moving parts and lessen chain wear. Corrosion caused by water ano abrasron by cart are the main sources of wear, which is attributed to removal of material increasing the hole size in the links and reducing the pin diameter thus creating a mismatch between an elongated chain and the teeth in a sprocket. Furthermore, friction is increased with the roughening of contact surfaces . Although much research has gone into the lubrication of industrial machines and automobiles, research into effective lubricants for bicycle chains has been much more limited. JP2019218427 teaches a lubricant for mobile devices, such as bicycles, said lubricant comprising a base oil, a solid lubricant, and a lubricating aid selected from water-soluble polymers and higher alcohols. US20210102139 describes a solid lubricant composition comprising paraffin wax, petroleum oil and molybdenum disulfide and its use in lubricating bicycle chains . There remains a need to provide improved bicycle chain lubricants which provide effective lubrication of a roller chain while decreasing friction and allowing better transfer of power from the rider to the wheels. Summary of the Invention The present invention provides a bicycle chain lubricant composition comprising a base oil; an anti-wear additive selected from the group consisting of zinc dialkyl dithiophosphates, molybdenum dithiocarbamates and mixtures thereof; and a tackifier. The present invention also provides a method for lubricating a bicycle chain, said process comprising the steps of applying to said chain a bicycle chain lubricant composition comprising a base oil; an anti-wear additive selected from the group consisting of zinc dialkyl dithiophosphates, molybdenum dithiocarbamates and mixtures thereof; and a tackifier. The present invention further provides the use in a bicycle chain lubricant, comprising a base oil and an anti-wear additive selected from the group consisting of zinc dialkyl dithiophosphates, molybdenum dithiocarbamates and mixtures thereof, of a tackifier for the purpose of improving the friction coefficient of the bicycle chain lubricant. Detailed Description of the Invention One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, not all features of an actual implementation may be described in the specification. When introducing elements of various embodiments of the present disclosure, the articles "a," "an," and "the" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to "one embodiment" or "an embodiment" of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. In the context of the present invention, in a case where a composition comprises two or more components, these components are to be selected in an overall amount not to exceed 100 mass%. The present inventors have found that the use of a tackifier in a bicycle chain lubricant provides a considerable improvement in the chain efficiency when used to lubricate the drive chain of a bicycle. The bicycle chain lubricant comprises a base oil. Preferably, said base oil is selected from those in Group V according to the API base oil classification. More preferably, the base oil is an ester base oil. The base oil is suitable incorporated into the bicycle chain lubricant in an amount of at least 90wt%, preferably at least 92wt%, based on the overall weight of the bicycle chain lubricant. The upper limit for the amount of base oil will be dictated by the amount of additives added to the lubricant. However, preferably no more than 99wt%, more preferably no more than 98wt% of base oil is present, based on the overall weight of the bicycle chain lubricant. The anti-wear additive is selected from the group consisting of zinc dialkyl dithiophosphates, molybdenum dithiocarbamates and mixtures thereof. of between C3 and C20. or secondary alkyl (1) Zinc dialkyldithiophosphates (ZnDTP), may be expressed by structural formula (1), below. In structural formula (1), R1, R2, R3 and R4 represent mutually independent hydrocarbon groups. Preferably they are primary or secondary alkyl groups More preferably, they are primary groups of between C3 and CIO. R1O / S sx OR3 y v , 2 . <\ / \ A R O s—Zn—S OR The content of the ZnDTP in the bicycle chain lubricant, if present is preferably in the range of from at least 0.025 to less than 0.250 wt%, based on the overall weight of the lubricant composition. The molybdenum dithiocarbamate (MoDTC) can be, for example, a molybdenum dialkyldithiocarbamate represented by formula (2) below. (2) In formula 2, R5 to R8 each denote an alkyl group, and Xi to X4 each denote an oxygen atom or sulfur atom. The alkyl groups R5, R6, R7 and R8 contained in the molybdenum dialkyldithiocarbamate represented by formula (2) are each independently a lipophilic group having 2-30 carbon atoms, and it is preferable for at least one of these four lipophilic groups to be a secondary lipophilic group. The molybdenum dithiocarbamate (MoDTC) used in the present aspect is preferably a molybdenum dithiocarbamate represented by formula (3) below. In formula (3), R5 to R8 each denote an alkyl group. The content of the molybdenum dithiocarbamate, if present, in the present bicycle chain lubricant composition is not particularly limited but if present is preferably in the range of from at least 0.025 to less than 0.250 wt%, based on the overall weight of the lubricant composition. The bicycle chain lubricant contains a tackifier. A tackifier is an additive that confers a tack or stringiness to lubricants and that is typically used to hold a lubricating oil in place where it is needed. Suitable tackifiers are high molecular weight polymers dissolved in oil. Preferably the high molecular weight polymers have a number average molecular weight of at least 100,000. Also preferably, the tackifier comprises a polyolefin copolymer (OCP) or polyisobutylene (PIB) dissolved in a base fluid. More preferably, the base fluid in a plant or vegetable oil. The tackifier is preferably incorporated into the bicycle chain lubricant in an amount in the range of from 0.1 to 2 wt% based on the overall weight of the bicycle chain lubricant. The invention will now be further illustrated by reference to the following non-limiting examples. Examples Four bicycle chain oil lubricants were formulated and blended as set out in Table 1 using the following formulation additives; base oil, anti-wear additive (s) and tackifier(s). Chain oil lubricant A contains a saturated polyol ester base oil, a zinc dialkyl dithiophosphate anti-wear additive and Tackifier A. Chain oil lubricant B contains a saturated polyol ester base oil, a molybdenum dithiocarbamate anti-wear additive and Tackifier A. Chain oil lubricant C contains a saturated polyol ester base oil, a mixture of two anti-wear additive(s), a zinc dialkyl dithiophosphate and a molybdenum dithiocarbamate; and Tackifier A. Chain oil lubricant D contains a saturated polyol ester base oil, a molybdenum dithiocarbamate anti-wear additive; and Tackifier B. Tackifier A is a partially biodegradable organic polyisoprene polymer in vegetable oil. Tackifier B is a biobased polymer in biodegradable triglyceride-based vegetable oil. Table 1 Lubricant Name Base Oil Anti-wear additive (s) Tackifier A (%) Tackifier B (%) Candidate A 95.51 2.49 2.0 — Candidate B 95.51 2.49 2.0 Candidate C 93.02 2.49* 2.49 2.0 — Candidate D 95.5 2.49 — 2.0 * 2.49wt% of each of a zinc dialkyl dithiophosphate and a molybdenum dithiocarbamate Friction and performance testing was carried out by the University of Bristol, Faculty of Engineering. The aim was to provide a performance evaluation for the four - 7 -lubricant formulations intended for use in competitive track cycling. All four lubricants were compared against a proprietary baseline product on the University of Bristol's chain drive dynamometer facility, developed especially for the testing of cycling hardware for high performance sport. Chain drive dynamometer tests were carried out across an envelope of operating points representing track cycling and power losses determined for each type of lubricant. The test rig is a Transmitted Power Measurement (TPM) or Full-load Test design which provides representative loading and boundary conditions for testing the chain drive system by closely replicating real-world conditions. In order for a fair test of the candidate lubricants, identical chains were prepared using a consistent method. There is no global standard for testing chains or their lubricants, beyond very fundamental tribological tests . Efficiency of a chain drive i.e. power lost is a function of both speed and force between the chain links. Efficiency varies with both speed and torque of the power input as well as other variables such as gear ratio, sprocket sizing, alignment and chain geometry. Transmission efficiency tests are arranged over a broad envelope of operating conditions defined in terms of input speed and torque. Chain drive dynamometer tests were carried out across an envelope of operating points representing track cycling and power losses determined for each type of lubricant, referred to as the duty cycle. A duty cycle mapped performance at input speeds from 70rpm to 130rpm in lOrpm steps and input torque of 23Nm to 161Nm in 23Nm steps. Torque input was additionally subject to a twice per input revolution sinusoidal revolution of +50% of the set-point value -representative of torque delivery of a male track cyclist. Resultingly, the power target at each set-point varies from 168W to 2190W. Three repeats of the duty cycle were made for each chain and to allow for a statistically relevant result to be produced. The results for transmission efficiency are presented as maps of power loss, referred to as Heat Maps, across the test envelope and recorded in Watts. Figure 1 provides an image for the test rig duty cycle used in the testing of the four Shell chain oil lubricants . Lubricants A to D were compared against a proprietary baseline product. The results of the Power Loss (Watts) and % transmission efficiency tests are shown in the two images shown in Figures 2 to 6. The heat maps shown in the Figures provide the Power loss (Watts) and % efficiency of each chain oil candidate lubricant at a given speed or torque. A decrease in Power loss (Watts), seen along the contours of the first heat map shown can be said to show an improvement in the efficiency of the lubricant from the baseline candidate lubricant tested. For example, the baseline lubricant shows 91.60W in the contour at the top right-hand side of the heat map image as shown in Figure 2. In comparison, chain oil lubricant A shows 57.78W in the same area of the heat map. This shows that Lubricant candidate A demonstrates an efficiency improvement in that area of the duty cycle - and the top right hand side of the heat map is a very extreme place to be, denoting the highest power and torque applied during the testing cycle. Table 2 shows the Maximum, minimum and Mean power lost in the chain across the speed and torque envelope as 5 presented in Figures 2 to 6. Table 2 Power (W) Baseline Lubricant A B C D Max 68.16 64.00 67.73 65.48 64.82 Mean 42.36 39.54 42.39 41.08 40.02 Min 22.23 20.45 22.52 21.74 21.07 Table 3 shows the amount of deviation from the baseline lubricant. Table 3 Deviation A B C D Max -4.16 -0.43 -2.68 -3.34 Mean -2.83 0.03 -1.28 -2.34 Min -1.78 0.29 -0.49 -1.16 Table 4. shows an overview of the power efficiencies for each lubricant candidate across the whole duty cycle map. 15 Table 4 Power Efficiency Baseline Lubricant B C D Max 96.74 96.91 96.75 96.82 96.88 Mean 94.10 94.46 94 . 03 94.16 94.30 Min 83.97 84.94 83.62 83.83 84.23 These chain oil lubricant candidates show improved performance in transmission efficiency against a proprietary baseline lubricant in all areas of the testing envelope and the formulations can be tailored 5 depending on the type of efficiency required. All of the candidate lubricant compositions demonstrate an advantage over the baseline lubricant, with chain oil candidate lubricants A &D each offering an average of 0.4% improvement in power transmission 10 efficiency across the whole heat map with candidate lubricant A giving almost 1% improvement in the lowest efficiency parts of the map. The inventors would like to extend their thanks to The University of Bristol, Faculty of Engineering for the 15 use of their specialised chain dynamometer testing rigs and the resulting data provided in support of this patent. - 11 -

Claims

1. A bicycle chain lubricant composition comprising a base oil; an anti-wear additive selected from the group consisting of zinc dialkyl dithiophosphates, molybdenum dithiocarbamates and mixtures thereof; and a tackifier.

2. The bicycle chain lubricant according to claim 1, wherein the base oil is an ester base oil, preferably a polyol ester base oil.

3. The bicycle chain lubricant according to claim 1 or claim 2, wherein, the anti-wear additive is present in an amount of A to B wt% based on the overall weight of the bicycle chain lubricant.

4. The bicycle chain lubricant according to any one of claims 1 to 3, wherein the tackifier comprises polymers having a number average molecular weight of at least 100,000 dissolved in a base fluid.

5. The bicycle chain lubricant according to claim 4, wherein the base fluid is a plant-based base fluid.

6. A method for lubricating a bicycle chain, said process comprising the steps of applying to said chain a bicycle chain lubricant composition comprising a base oil; an anti-wear additive selected from the group consisting of zinc dialkyl dithiophosphates, molybdenum dithiocarbamates and mixtures thereof; and a tackifier.

7. Use in a bicycle chain lubricant, comprising a base oil and an anti-wear additive selected from the group consisting of zinc dialkyl dithiophosphates, molybdenum dithiocarbamates and mixtures thereof, of a tackifier for the purpose of improving the friction coefficient of the bicycle chain lubricant.

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