WO2012042267A1

WO2012042267A1 - Rubber composition for use in tension belts

Info

Publication number: WO2012042267A1
Application number: PCT/GB2011/051851
Authority: WO
Inventors: Mike Heslop; Nagarajan Chellachamy; Peter Mackrell
Original assignee: Icon Polymer Limited
Priority date: 2010-09-30
Filing date: 2011-09-29
Publication date: 2012-04-05
Also published as: GB201016463D0

Abstract

A rubber composition for providing a tension belt with reduced tension decay and a longer life-span.

Description

RUBBER COMPOSITION FOR USE IN TENSION BELTS

Description

The present invention relates to a rubber composition and a belt using the rubber composition. In particular, the present invention relates to a tension belt suitable for use in a vacuum cleaner.

Rubber tension belts are used extensively in the vacuum cleaning industry to drive various components in vacuum cleaners. As an example, in the classic upright vacuum cleaner design, a rubber belt connects a motor drive shaft and a brushbar either directly or through a clutch mechanism. The rubber belt is then used to transmit power from the vacuum cleaner's motor to rotate the brushbar which then loosens dirt and dust in the carpet so that it can be pulled into the vacuum cleaner's air flow. It is common with this type of belt, however, that over time and during normal operation the belt experiences tension decay, becomes permanently deformed and consequendy, the belt loses tension. If the tension of the belt drops below a certain level, the belt will stop transmitting power to the brushbar and the vacuum cleaner will fail to work. In order to offset this tension loss, the belts are generally fitted at high installation tensions. However this puts an increased load on the bearings and other fittings inside the vacuum cleaner and can lead to excessive pulley wear.

Furthermore, typically used rubber tension belts often have a tendency to crack or chunk prematurely in normal operation due to high operating temperatures as a result of rapid internal heat generation. This chunking phenomenon is particularly prevalent in systems where the belt has to operate on an aggressive platform, i.e., where the operating temperature of the belt is over 70°C.

Therefore, there remains a need for a rubber tension belt which can be used in a vacuum cleaner which exhibits reduced tension decay and a longer life-span. In addition, it would be desirable to provide a rubber tension belt which has an improved resistance to stall failure, a lower running temperature and reduced age hardening. Accordingly, in a first aspect of the invention there is provided a rubber composition comprising: (a) 100 parts of polychloroprene rubber; (b) 0.1 to 5 PPHR of an organic peroxide; and (c) 1.0 to 4.5 PPHR of a multifunctional co-agent. In an embodiment of the invention, the decomposition temperature of the organic peroxide may be between about 90°C to 170°C. In the rubber composition, the organic peroxide may be a symmetrical peroxide. In a further embodiment, the organic peroxide may be a diaralkyl peroxide, such as dicumyl peroxide. In another embodiment of the invention, the multifunctional co-agent is a non-sulfur co- agent. In the rubber composition, the multifunctional co-agent may be selected from the group consisting of acrylate esters, methacrylate esters, zinc salts of acrylic acid, zinc salts of methacrylic acid and dimaleimides. In one embodiment of the invention, the

multifunctional co-agent is a dimaleimide.

In an embodiment of the invention, the rubber composition may further comprise at least one metallic oxide. In another embodiment, the rubber composition may comprise a mixture of metallic oxides. In a further embodiment, the rubber composition may comprise at least 5 to 14 PPHR of the at least one metallic oxide.

In an embodiment of the invention, the composition of the first aspect of the invention may comprise at least one antioxidant or antidegradant.

In a further embodiment of the invention, the rubber composition may comprise at least one antioxidant and at least one antidegradant. In the rubber composition, the antioxidant may be a secondary aromatic amine or a substituted phenol. In a further embodiment, the rubber composition may comprise 2 to 8 PPHR of the at least one antioxidant or antidegradant. Furthermore, in another embodiment of the invention, the composition of the first aspect of the invention may comprise at least one process oil. In an embodiment of the invention, the process oil may be a naphthenic, paraffinic or aromatic-based oil or a mixture thereof. In a further embodiment, the process oil may be an ether or ester-based plasticizer or a mixture thereof. In an embodiment the at least one process oil may be selected from tri- ethylene glycol ester and 5,8,11,13,16,19-hexaoxatricosane. In a still further embodiment, the rubber composition of the present invention may comprise 10 to 20 PPHR of the process oil. In an embodiment, the composition may comprise one process oil.

In an embodiment of the invention, the rubber composition may comprise a filler. In a further embodiment of the invention, the rubber composition may comprise 36 to 76 PPHR of carbon black. In a further embodiment of the invention, the rubber composition may comprise a petroleum wax. In an embodiment of the invention, the rubber composition may comprise 0.1 to 3 PPHR of paraffin wax.

In another embodiment, the rubber composition may further comprise a fatty acid. In an embodiment of the invention, the rubber composition may comprise 0.5 to 3 PPHR of the fatty acid.

In a second aspect, there is provided a method of preparing a polychloroprene rubber compound for use in a tension belt, which may comprise the steps of providing the rubber composition of the first aspect of the invention, and curing the rubber composition.

In a third aspect, there is provided a tension belt formed from the rubber composition of the first aspect of the invention. In a fourd aspect of the invention, the rubber composition of the invention is used for the manufacture of a tension belt.

The tension belts according to d e present invention exliibit improved resistance to stall failure, have reduced tension decay, operate at a lower running temperature, have reduced hardness changes during the life of the belt and have a reduced susceptibility to chunking.

Further embodiments of the present invention in any of its various aspects are as described below or as defined in the dependent claims. A more complete appreciation of the present invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, wherein:

FIGURE 1 shows the tension decay experienced over time by a belt manufactured with a rubber compound according to an embodiment of the present invention, compared with a belt manufactured with a conventional rubber compound.

FIGURE 2 depicts the measured percentage stretch from nominal internal diameter against time on the test floor for an aggressive platform.

FIGURE 3 depicts belt failure due to chunking after 329 hours of testing the belt manufactured with the conventional rubber compound.

FIGURE 4 depicts a belt manufactured with a conventional rubber compound showing chunking after 820 hours of use. FIGURE 5 shows the tension decay experienced over time by a belt manufactured with a rubber compound according to an embodiment of the present invention, compared with a belt manufactured with a conventional rubber compound.

FIGURE 6 shows the tension decay experienced over time by a belt manufactured with a rubber compound according to an embodiment of the present invention, compared with a belt manufactured with a conventional rubber compound.

The rubber composition according to the present invention comprises: (a) 100 parts of polychloroprene rubber; (b) 0.1 to 5 parts by mass of an organic peroxide; and (c) 1.0 to 4.5 PPHR of a multifunctional co-agent.

The term 'polychloroprene rubber' refers to a polymer composed of repeating structural units derived from a base monomer of 2-chloro-l,3-butadiene. The term 'PPHR' stands for parts by weight per hundred parts of rubber. The unit is used to define the quantity of an ingredient used in a rubber formulation relative to a total of 100 parts of the rubber component used in the formulation.

According to an embodiment, in the rubber composition, the organic peroxide has a decomposition temperature of between about 90°C to 170°C. In another embodiment the organic peroxide is a symmetrical peroxide, i.e. R-O-O-R, where each R group is the same. Suitable organic peroxides include, but are not limited to, diaralkyl peroxides, diaryl peroxides, diacyl peroxides, dialkyl peroxides, peroxyketals, monoperoxy carbonates, acetyl alkylsulfonyl peroxides, dialkyrperoxydicarbonates, tert-alkyl hydroperoxides, peroxy esters, and acetyl alkylsulfonylperoxides.

For example, the organic peroxide may be: di-cumyl peroxide; tert-butyl cumyl peroxide; 2,5-dimethyl-2,5 bis(tertbutyl peroxy)hexyne-3; bis (tert-butyl peroxy isopropyl)benzene; 4,4-di-tert-butyl peroxy N-butyl valerate; l,l-di-tert-butylperoxy-3,3,5- trimethylcyclohexane; bis- (tert-butyl peroxy)-diisopropyl benzene; t-butyl perbenzoate; di- tert-butyl peroxide; 2,5-dimethyl-2,5-di-tert-butylperoxide hexane, and combinations thereof.

In the rubber composition of the present invention the amount of organic peroxide may be from 0.1 to 5 PPHR.

In an embodiment of the invention, the organic peroxide is dicumyl peroxide.

The peroxide used for vulcanising the rubber may be provided and used on an inert carrier such as, for example, clay, calcium carbonate, carbon black or a binder.

In the context of the present invention, the term 'multifunctional co-agent' refers to a compound having multiple functionality that is capable of increasing both the rate and the state of the cure. For example, the compound may favour network formation through increased local concentrations of easily-abstractable allylic hydrogens or other very reactive sites of unsaturation. Typically, the multifunctional co-agent is capable of performing at least one ancillary function in the composition in addition to its properties as a curative, such as, for example, as an anti-scorching agent or keying agent.

The multifunctional co-agent may be a non-sulfur containing co-agent. Examples of the multifunctional co-agent may include: maleimides, such as, N, N'-(m-Phenylene) climaleimide, 1,2-phenylene dimaleimide, 1,4-phenylene dimaleimide and 1,3- Bis(cittaconimidomethyl)benzene; acrylates, such as octyl/ decyl acrylate, 3-chloro-2- hydroxypropyl methacryulate, oligoester acrylate; cyanurates, such as triallyl cyanurate and triallyl isocyanurate; and anhydrides, such as, maleic anhydride and succinic anhydride and combinations thereof. However, the multifunctional co-agent is not limited thereto.

For example, a rubber composition comprising N, N'-(m-Phenylene) dimaleimide is particularly suitable. The amount of the multifunctional co-agent used in the rubber composition of the present invention may be from about 1.0 to 4.5 PPHR.

The rubber composition may include at least one metallic oxide. Any metallic oxide suitable for acting as an activator in a peroxide curing system can be employed. Examples of suitable metallic oxides include, but are not limited to, MgO, ZnO, active ZnO, CaO, BaO, PbO, Pb₃0₄ and A1₂0₃. Examples of the metallic oxide may also include mixtures or alloys of at least two kinds of the metallic oxides described above. In an embodiment of die invention, the amount of metallic oxide may be from about 0.5 to 25 PPHR, or from about 5 to 14 PPHR, or from about 6 to 10 PPHR.

In a further embodiment, the metallic oxide may be a mixture of MgO and ZnO. In the rubber composition of the present invention the amount of MgO and ZnO may be from about 2 to 6 PPHR and from about 3 to 8 PPHR, respectively.

In an embodiment, the rubber composition may include at least one antioxidant or antidegradant. The antioxidant may be a secondary amine or a substituted phenol.

The term 'antioxidant' relates to compounds that inhibit or prevent the oxidative breakdown of polymers and/ or inhibit or prevent reactions that are promoted by oxygen radicals. Any secondary aromatic amine or substituted phenol suitable for acting as an antioxidant can be employed. Examples of suitable antioxidants include, but ate not limited to, alkylene-bis-alkyl substituted cresols, substituted phenols, alkylene bisphenols, alkylene trisphenols and secondary aromatic amines, such as, N'-Diphenyl-para-phenylenediarnine, N-Isopropyl-N'-phenyl-para-phenylenediaiTiine, N-(l,3-dimethylbutyl)-N'-phenyl-para- phenylene<iiamine and Ν,Ν'-dHsooctyl-para-phenylenecliamine. For example, the antioxidant of the present invention may be N-Isopropyl-N'-phenyl-para- phenylenediamine.

The amount of antioxidant may be from about 0.5 to 8 PPHR, or from about 1 to 4 PPHR, or from 1.5 to 3 PPHR.

According to an embodiment, the rubber composition may comprise at least one antioxidant and at least one antidegradant. The term 'antidegradant' as used herein is taken to mean an ingredient added to rubber compounds to deter the aging of the rubber compound. Any compound suitable for acting as an antidegradant in a peroxide curing system can be employed. Examples of suitable antidegradants include, but are not limited to, P-phenylene ctiamines, thiophosphates and substituted triazines. For example, the antidegradant may be N-(1,3-Dimethylbutyl)-N'- phenyl-p-phenylene diamine.

The amount of the antidegradant may be from about 0.5 to 8 PPHR, or from about 1 to 4 PPHR, or from about 1.5 to 3 PPHR. The rubber composition of the present invention may include process oil, which may be blended with the rubber. The process oil acts as a plasticizer, and may reduce the hardness of the rubber by enhancing its plasticity. Suitable process oils may include, but are not limited to, naphthenic, paraffinic or aromatic-based oils, petroleum or vegetable oils and ether or ester-based plasticizers. For example, the process oil may be at least one of 5,8,11,13,16,19- hexaoxatricosane and tri-ethylene glycol ester. The plasticizer may be a phthalate ester, a sebacate or an oleate. In an embodiment of the invention, the amount of process oil in the rubber composition may be from about 5 to 40 PPHR, or from about 10 to 20 PPHR, or from 11 to 15 PPHR.

In one embodiment of the invention, the rubber composition may further comprise a reinforcing agent or filler. Such a compound may be added to the rubber composition as a low cost diluent or in order to modify the rubber product's wear resistance and strength. Suitable reinforcing agents or fillers that may be used include carbon black, silica, clay, chalk, talc, wollastonite, aluminium hydroxide, magnesium hydroxide and calcium carbonate.

Thus, the rubber composition of the present invention may comprise carbon black. The amount of carbon black added to the rubber formulation may be from 1 to 80 PPHR, or from 36 to 76 PPHR, or from 50 to 60 PPHR. The carbon black particles can be of any suitable diameter. In particular, the average diameter of the carbon black particles can be from 1,000 to 10,000 nm, or from 100 to 1000 nm, or from 10m to 100 nm.

The rubber composition of the present invention may include a fatty acid. The fatty acid may be a linear fatty acid, a branched fatty acid or a derivative of a fatty acid. Suitable fatty acids may include fatty acids having from 4 to 24 carbon atoms, in particular from 8 to 18 carbon atoms.

For example, the fatty acid may include butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, pelargonic acid, capric acid, myristic acid, pentadecylic acid, palmitic acid, heptadecanoic acid, stearic acid, oleic acid, maleic acid, linoleic acid and linolenic acid.

The rubber composition of the present invention may comprise stearic acid. The amount of stearic acid may be from 0.5 to 6 PPHR, or from about 1 to 3 PPHR.

The rubber composition of the present invention may include a petroleum wax or a microcrystalline wax, which may be added to the rubber compound in a small amount to influence the performance of the compound in factory processes, or to enhance physical properties by aiding filler dispersion. The wax may also act as a rubber extender or softener to enhance the properties of the rubber compound. For example, the rubber composition of the present invention may include paraffin wax. The paraffin wax may be added to the rubber composition in an amount of 0.1 to 6 PPHR, or from 0.1 to 3 PPHR, or from 0.5 to 1 PPHR.

Other conventional rubber additives, such as, lubricants, tackifiers, waxes, dye pigments, UV-stabilization agents, blowing agents, nucleating agents, voltage stabilizers, metal deactivators, coupling agents and flame retardants may also be employed in their usual amounts either alone or in combination.

In an embodiment of the invention, the rubber composition may comprise: 100 parts of polychloroprene rubber; 0.1 to 5 PPHR of an organic peroxide; 1.0 to 4.5 PPHR of a multifunctional co-agent; 5 to 14 PPHR of at least one metallic oxide; 2 to 8 PPHR of at least one antioxidant or antidegradant; 10 to 20 PPHR of a process oil; 36 to 76 PPHR of carbon black; 0.5 to 3 PPHR of a fatty acid; and 0.1 to 3 PPHR of paraffin wax.

The polyisoprene rubber may also be copolymerized with another polymer such as, natural rubber, polybutadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, butylrubber, acrylic rubber, ethylene-alpha-olefin rubber, low density polyethylene, straight chain low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene or the like.

The rubber compositions of this invention are prepared by mixing or compounding the ingredients according to conventional rubber compounding or mixing techniques.

The rubber composition described above may be used in the manufacture of a tension belt in accordance with the present invention in its second aspect.

The term 'belt' as used herein, is taken to mean a loop of flexible material used in a belt drive system to transmit motion. The term 'belt' thus encompasses flat belts, round belts, vee belts, multi-groove belts, ribbed belts, film belts and timing belts. The term 'tension belt' as used herein is taken to mean a belt which is used to transmit power or motion from one part to another.

The term 'flat belt' as used herein is taken to mean a belt consisting of a flat loop of material used to transmit motion between, for example, two pulleys.

The present invention will be described in further detail with reference to examples and comparative examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

Synthesis Example 1: Preparation of Rubber Compound A

The ingredients of the formulation detailed in Table 1 were mixed in a 75 litre K4 Carter Mixer until the discharge temperature of 105°C was reached. The product was then shaped into a belt which was then subjected to various tests in order to measure the physical properties of the belt. The results of the analysis of the test belt and a conventional rubber compound are shown in Tables 1 to 7 and Figures 1 to 4.

Table 1: Formulation of the test belt A

Ingredient PPHR

Polychloroprene 100.000

Carbon black 55.000

Magnesium Oxide 4.000

Stearic Acid 1.000

N-Isopropyl-N'-phenyl-p-phenylene diamiiie 2.000

Zinc Oxide 5.000

N-(l,3-Dimediylbutyl)-N'-phenyl-p-phenylene

diamine 2.000

Paraffin Wax 0.500

Dicumyl peroxide 2.000

N, N'-(m-Phenylene) dimaleimide 1.500

Polyefher 12.000

Total 185.000 Comparative Synthesis Example 1: Preparation of a Conventional Rubber

Compound

For comparison, a conventional rubber belt was made by die same methodology as for the test belt, with the exception that the ingredients and quantities according to the formulation detailed in Table 2 were used.

Table 2: Formulation of the conventional rubber compound

Mixing Method

The mixing metiiods used in Syndiesis Example 1 and Comparative Synthesis Example 1 were all according to the following mixing specifications:

1) Rotor speed: 60 rpm

2) Set pressure: 100 psi

3) Discharge temperature (max): 105°C

4) Charging specifications:

0': rubber ingredient

50": carbon black

Γ40": process oil 1'55": magnesium oxide, zinc oxide, stearic acid, antioxidant, antidegradant, paraffin wax, organic peroxide and curative

2Ί0": raising and lowering of ram The rubber product was then processed through an extruder, to form a rubber tube which was then cured in an autoclave. The cured rubber tube was then cut into a belt and assembled in either a 110V Dirt Devil Featherlight® vacuum cleaner, a 230V VAX Power 3® vacuum cleaner, a 230V VAX Power 5® vacuum cleaner or a test rig. Evaluation of rubber belt performance

The performance of a rubber belt manufactured with the compound obtained in Synthesis Example 1 was measured and evaluated in d e following manner:

Experimental Examples 1 - 3: Stall Test Analysis Evaluation Results

In order to determine the length of time that a belt manufactured from the rubber compound obtained in Synthesis Example 1 is able to withstand before breaking when the brushroll and the belt are stopped but when the motor shaft is still spinning, a test rig was used for stall test analysis. The test rig was used to replicate die set up of the motor shaft and brushroll in 3 different vacuum cleaners: a 110V Dirt Devil Featherlight®, a 230V VAX Power 3® and a 230V VAX Power 5®.

Experimental Example 1 - 110V Dirt Devil Featherlight®

For stall test analysis, a belt manufactured from the rubber compound obtained in

Synthesis Example 1, was looped around two pulleys with a diameter of 7.1mm and 34mm, respectively. The distance between the two pulleys was set to 178mm. One of die pulleys was connected to a 120V, 50/ 60 Hz motor. The motor was run for 10 seconds before d e brushbar was artificially locked to invoke a stall condition. The time taken for the belt to break was then measured. Experimental Example 2 - 230V VAX Power 3®

Stall test analysis of a belt manufactured from the rubber compound obtained in Synthesis Example 1 and installed in a 230V VAX Power 3® vacuum cleaner was performed as for the 110V Dirt Devil Featherlight® vacuum cleaner, with the exception that the distance between the two pulleys was set at 190mm.

Experimental Example 3 - 230V VAX Power 5®

Stall test analysis of a belt manufactured from the rubber compound obtained in Synthesis Example 1 and installed in a 230V VAX Power 5® vacuum cleaner was performed as for the 110V Dirt Devil Featherlight® vacuum cleaner, with the exception that the distance between the two pulleys was set at 200mm.

Results of the stall test analysis are shown in Table 3 below: For comparison, a belt manufactured from a standard rubber compound was also included in the study, the results of which are also shown in Table 3.

Table 3: Stall test analysis for flat belts manufactured from the rubber compound obtained in Synthesis Example 1 and Comparative Synthesis Example 1.

* Average of 10 measurements.

The percentage improvement when using a belt manufactured from the rubber compound obtained in Synthesis Example 1, over a belt manufactured from a conventional rubber compound was calculated, the results of which are shown in Table 4 below: Table 4: Percentage improvement when using a belt manufactured from the rubber compound obtained in Synthesis Example 1, over a belt manufactured from a conventional rubber compound.

From tliis data it is evident that belts manufactured from the rubber compound according to the present invention, are on average 31% better in terms of resistance to stall than those manufactured from the conventional rubber compound. Experimental Example 4 - Tension Decay analysis

For tension decay analysis, a 110V Dirt Devil Featherlight® vacuum cleaner, a 230V VAX Power 3® vacuum cleaner and a 230V VAX Power 5® vacuum cleaner were each fitted with a belt manufactured from the rubber compound obtained in Synthesis Example 1. The vacuum cleaners were used on a moving carpet for a period of lhr, 24hr, 168hr, 500hr and 850hr before the belts were removed from the vacuum cleaners. After 30 minutes the tension decay experienced by the belts was evaluated using a Hampden tension tester.

A comparison of d e tension decay experienced by the belt manufactured with the rubber compound obtained in Synthesis Example 1 and used in a 110V Dirt Devil Featherlight® vacuum cleaner and the tension decay experienced by a belt manufactured with die conventional rubber compound and used in the same vacuum cleaner, is shown in Figure 1. As illustrated in Figure 1, over the first hour the tension of die standard belt drops from 57N to 48N (a difference of 9N), whereas the tension of the belt manufactured with the rubber compound of the present invention drops from 48.3N to 44N (a difference of 4.3 N). Over a period of 336 hours, the tension drops are 20N and 7.8 N, respectively. The tension decay experienced by the rubber belts manufactured with the rubber compound of the present invention and installed in a 230V VAX Power 3® vacuum cleaner and a 230V VAX Power 5® vacuum cleaner, are shown in Table 5 below. For comparison, die tension decay experienced by a stock belt and a belt manufactured from the conventional rubber compound and tested in a 230V VAX Power 3® vacuum cleaner and a 230V VAX Power 5® vacuum cleaner were also included in die study, the results of which are also shown in Table 5 below:

Table 5: Tension decay experienced by the test rubber belt, the conventional belt, and the stock belt over time when used in a 230V VAX Power 3® vacuum cleaner and a 230V VAX Power 5® vacuum cleaner.

* Tension decay after 750 hours. From this data it is evident that belts made out of d e rubber compound of the present invention retained their tension to a greater degree tiian tiiose made out of a conventional rubber compound.

Experimental Example 5 - Percentage stretch analysis

For percentage stretch analysis, die belts were used in a 230V VAX Power 3® vacuum cleaner, a 230V VAX Power 5® vacuum cleaner and a 110V Dirt Devil Fea herlight® vacuum cleaner on a moving carpet for set periods of time. The stretch of the belt was then measured on a calibrated cone, which had a resolution of 1mm. The results of the stretch analysis can be seen in Figure 2. Experimental Example 6 - Running temperature analysis

The average and maximum running temperatures of a 110V Dirt Devil FeatherUght® vacuum cleaner, a 230V VAX Power 3® vacuum cleaner and a 230V VAX Power 5® vacuum cleaner fitted with a belt manufactured with the rubber compound obtained in example 1 were measured. For comparison, die running temperature of the vacuum cleaners fitted with a stock belt and a belt manufactured with the conventional rubber compound, were also included in the study, the results of which are shown in Table 6 below: Table 6: Maximum running temperature of a 110V Dirt Devil Featherlight® vacuum cleaner, a 230V VAX Power 3® vacuum cleaner and a 230V VAX Power 5® vacuum cleaner when fitted with a belt manufactured with the rubber compound obtained in Synthesis Example 1 and a belt manufactured with the conventional rubber compound.

From this data it is evident that both the maximum running temperature and the average running temperature of the vacuum cleaners fitted with the belt manufactured from the rubber compound of the present invention are lower than that of the vacuum cleaners fitted with a belt manufactured from the conventional rubber compound. This is a consequence of the fact that the belt manufactured with the rubber compound of the present invention does not generate internal heat as quickly as the conventional rubber belt, and therefore operates at a lower overall running temperature. This in turn, reduces the heat ageing affect on the belt.

Experimental Example 7 - Hardness ageing of the belts

The hardness of the belt manufactured from the rubber compound of the present invention was determined by a handheld International Rubber Hardness Degrees meter (IRHD).

A comparison of the hardness of a belt manufactured from the rubber compound obtained in Synthesis Example 1, a belt manufactured from the conventional rubber compound and a stock belt provided with the 230V VAX Power 3® and 230V VAX Power 5® vacuum cleaners, is shown in Figure 3 and Table 7 below.

Table 7: Belt hardness experienced by the test rubber belt, the conventional belt, and the stock belt over time, when used in a 110V Dirt Devil Featherlight® vacuum cleaner, a 230V VAX Power 3® vacuum cleaner and a 230V VAX Power 5® vacuum cleaner.

* IRHD change after 750 hours.

**IRHD change after 400 hours. Experimental Example 8 - Life cycle analysis

For life-cycle analysis, a 110V Dirt Devil Featherlight® vacuum cleaner, a 230V VAX Power 3® vacuum cleaner and a 230V VAX Power 5® vacuum cleaner were each fitted with a belt manufactured from the rubber compound obtained in Synthesis Example 1.

The vacuum cleaners were used on a moving carpet for a period of 8— 10 minutes before being removed from the carpet for 2 minutes. This process was repeated for a set period of time. After 345 hours it was found that the comparative belt installed in the 110V Dirt Devil

Featherlight® vacuum cleaner failed. Upon analysis of the belt it was found that the failure mode was due to chunking of the belt, wherein the belt had hardened during operation, become more britde and chunks of the material had delaminated from the outer face of the rubber. The chunking experienced by the comparative belt is illustrated in Figure 3.

In comparison, it was found that the test belt manufactured from the rubber compound of die present invention and installed in a 110V Dirt Devil Featherlight® vacuum cleaner was yet to fail after 750 hours of the testing cycle detailed above. With die 230V VAX Power 3® and 5 vacuum cleaners, both the comparative belt and test belt lasted 850 hours without breaking. However, upon analysing the belts, it was apparent that the belt manufactured from the conventional rubber compound and installed in the 230V VAX Power 5® vacuum cleaner, was beginning to display chunldng after 820 hours of operation. This is illustrated in Figure 4.

As shown in the Examples, a tension belt manufactured with the rubber composition according to the present invention exhibits improved resistance to tension decay, reduced stall failure and increased thermal stability. Thus, the tension belt manufactured with the rubber composition of the present invention may be used in vacuum cleaners, where such properties are desirable.

Whilst the present invention has been described in connection with certain exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

Synthesis Example 2: Preparation of Rubber Compound B

The ingredients of the formulation detailed in Table 8 were mixed in a 85 litre K4 Carter Mixer until the discharge temperature of 105°C was reached. The product was then shaped into a belt which was then subjected to various tests in order to measure the physical properties of the belt. The results of the analysis of the test belt and a conventional rubber compound are shown in Tables 8 to 11 and Figures 5 to 6.

Table 8: Formulation of the Test Belt B

Evaluation of rubber belt performance

The performance of a rubber belt manufactured with the compound obtained in Synthesis Example 2 was measured and evaluated in the following manner: Expeiimental Example: Life Cycle Testing

A comparison of the life cycle of a belt manufactured with the rubber compound obtained in Synthesis Example 2 and that used in a conventional vacuum cleaner, is shown in Tables 9 and 10.

Table 9: Life Cycle Testing analysis for a belt manufactured from the rubber compound obtained in Synthesis Example 2 and a conventional belt.

Table 10: Life Cycle Testing analysis for a belt manufactured from the rubber compound obtained in Synthesis Example 2 and a conventional belt.

Wall Gauge Test

Tension

Belt min max

(N) Type Result

(mm) (mm)

51 hrs Belt

Test Belt B 2.04 2.38 59 Life Test

ground

Conventional 17 hrs Belt

1.99 2.21 60 Life Test

Belt ground

Test Belt B 2.13 2.46 60 Life Test 438 hrs stopped

Test Belt B 2.06 2.38 61 Life Test 260 hrs stopped

Test Belt B 2.15 2.45 62 Life Test 264 hrs stopped Test Belt B 2.08 2.38 63 Life Test 247 his stopped

Test Belt B 2.09 2.43 62 Life Test 247 hrs stopped

Test Belt B 2.07 2.42 63 Life Test 261 hrs stopped

Test Belt B 2.11 2.32 63 Life Test 215 his stopped

Test Belt B 2.05 2.48 63 Life Test 215 his running

Test Belt B 2.14 2.39 64 Life Test 215 hts stopped

Test Belt B 2.04 2.38 64 Life Test 215 hts running

Conventional

Belt 1.98 2.12 61 Life Test 172 hrs stopped

Conventional

Belt 1.97 2.15 61 Life Test 172 hrs stopped

From this data it is evident that the belts manufactured from the rubber compound according to an embodiment of the present invention outperforms the conventional belts in the life cycle testing.

Experimental Example - Tension Decay Analysis

For Tension decay analysis, a conventional vacuum cleaner was fitted with a belt manufactured from the rubber compound obtained in Synthesis Example 2. The tension decay of the belts was then measured during a fatigue cycle.

The tension decay experienced by the belt manufactured with the rubber compound obtained in Synthesis Example 2 compared with that used in a conventional vacuum cleaner, is shown in Figures 5 and 6.

As illustrated in Figures 5 and 6, the belts made of the rubber compound according to an embodiment of the present invention retained their tension to a greater degree than those made out of a conventional rubber compound.

Experimental Example— Burn-through Resistance

Burn-through resistance analysis was carried out using a rag to stall the brush bar of a test rig set-up to replicate the set-up of the motor shaft and brushroll in a conventional vacuum cleaner. The machine was allowed to cool between each test. Times were taken from the brush bar becoming stationary to the belt snapping.

The results are illustrated in table 11.

► 5

Table 11— Burn-through Resistance Analysis for a belt manufactured from the rubber compound obtained in Synthesis Example 2 and for a conventional belt.

Burn

Tension

Belt Through

(N)

( Sec)

Test Belt B 63 33.93

Test Belt B 61 34.64

Test Belt B 65 30.51

Test Belt B 63 31.25

Test Belt B 63 31.09

Test Belt B 62 31.68

Test Belt B 63 32.6

Test Belt B 63 31.52

Test Belt B 62 30.35

Test Belt B 63 33.84

Average Burn-through (sec) 32.14

Maximum Burn-through (sec) 34.64

Minimum Burn-through (sec) 30.35

Burn

Tension

Belt Through

( )

( Sec)

Conventional Belt 58 23.35

Conventional Belt 60 26.00

Conventional Belt 60 23.31

Conventional Belt 67 28.75

Conventional Belt 65 27.26 Average Burn-through (sec) 25.73

Maximum Burn-through (sec) 28.75

Minimum Burn-through (sec) 23.31

From this data it is evident that belts manufactured from the rubber compound according to an embodiment of the present invention, are on average 25% better in terms of burn- through resistance than a conventional belt.

Claims

1. A rubber composition comprising: (a) 100 parts of polychloroprene rubber; (b) 0.1 to 5 PPHR of an organic peroxide; and (c) 1.0 to 4.5 PPHR of a multifunctional co-agent.

2. A rubber composition as claimed in claim 1, wherein the decomposition temperature of the organic peroxide is between about 90°C to 170°C.

3. A rubber composition as claimed in claim 2, wherein the organic peroxide is a symmetrical peroxide.

4. A rubber composition as claimed in any one of claims 1 to 3, wherein the organic peroxide is diaralkyl peroxide.

5. A rubber composition as claimed in any one of the preceding claims, wherein the multifunctional co-agent is a non-sulfur co-agent.

6. A rubber composition as claimed in any one of the preceding claims, wherein the multifunctional co-agent is selected from the group consisting of acrylate esters, methacrylate esters, zinc salts of acrylic acid, zinc salts of methacrylic acid and

dimaleimides.

7. A rubber composition as claimed in claim 6, wherein the multifunctional co-agent is a dimaleimide.

8. A rubber composition as claimed in any one of the preceding claims, further comprising at least one metallic oxide.

9. A rubber composition as claimed in claim 8, which comprises a mixture of metallic oxides.

10. A rubber composition as claimed in claims 8 or 9, which comprises 5 to 14 PPHR of the at least one metallic oxide.

11. A rubber composition as claimed in any one of the preceding claims, further comprising at least one antioxidant or antidegradant.

12. A rubber composition as claimed in claim 11, which comprises at least one antioxidant and at least one antidegradant.

13. A rubber composition as claimed in claims 11 or 12, wherein the at least one antioxidant is a secondary aromatic amine or a substituted phenol.

14. A rubber composition as claimed in claims 11, 12 or 13, which comprises 2 to 8 PPHR of the at least one antioxidant or antidegradant.

15. A rubber composition as claimed in any one of the preceding claims, further comprising at least one process oil.

16. A rubber composition as claimed in claim 15, wherein the at least one process oil is a naphthenic, paraffinic or aromatic-based oil.

17. A rubber composition as claimed in claim 15, wherein the at least one process oil is an ether or ester-based plasticizer.

18. A rubber composition as claimed in claims 15, 16 or 17, which comprises 10 to 20 PPHR of the at least one process oil.

19. A rubber composition as claimed in any one of the preceding claims, further comprising a filler.

20. A rubber composition as claimed in claim 19, which comprises 36 to 76 PPHR of carbon black.

21. A rubber composition as claimed in any one of the preceding claims, further comprising of a petroleum wax.

22. A rubber composition as claimed in claim 21, which comprises 0.1 to 3 PPHR of paraffin wax.

23. A rubber composition as claimed in any one of the preceding claims, further comprising a fatty acid.

24. A rubber composition as claimed in claim 23, which comprises 0.5 to 3 PPHR of the fatty acid.

25. A method of preparing a polychloroprene rubber compound for use in a tension belt, which comprises the steps of providing a rubber composition as claimed in any one of claims 1 to 24, and curing the rubber composition.

26. A tension belt formed from a rubber composition as claimed in any one of claims 1 to 24.

27. Use of a rubber composition as claimed in any one of the preceding claims for the manufacture of a tension belt.