Patent Publication Number: US-2023151851-A1

Title: Low friction slide member

Description:
This application is a continuation of U.S. application Ser. No. 15/757,541 filed Mar. 5, 2018, which is a national phase of International Application No. PCT/SE2016/050835 filed Sep. 7, 2016, and claims priority to Swedish Application No. 1551138-9 filed on Sep. 7, 2015 and Swedish Application No. 1651049-7 filed on Jul. 13, 2016, which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a slide member, e.g. a slide bar or a sliding part, having a sliding layer with low friction. Further, the invention relates to a sliding system comprising such a slide member. Such sliding systems may for example be used in sliding door arrangements, extendable tables, kits for hanging curtains, and sliding drawer arrangements. 
     BACKGROUND 
     Wardrobes having sliding doors are well-known in the art (cf. e.g. DE 298 13 478). Typically, the doors are arranged with supportive ball bearings, e.g. wheels rolling over a rail, at the upper end of the door and steering means, e.g. pins, at the lower. Ball bearings are working well, but suffer from being somewhat dust sensitive. Further, the start-stop resistance is very low if the doors are to be easily moveable; an inherent feature of ball bearings. At the end-positions, this may be partly overcome by providing resting end-positions provided with e.g. heads or recesses, for the wheels. However, this would not overcome the low start-stop resistance at intermediate positions. 
     Sliding kitchen doors, being less heavy than wardrobe sliding doors, are typically not provided with ball bearings, but are mounted standing in a sliding groove, i.e. a linear plain bearing. For lighter doors this may work well, though the sliding resistance may be fairly high; especially at start. However, for heavier doors, e.g. wardrobe sliding doors, linear plain bearings typically provide too high sliding resistance for practical use; especially at start. Further, such linear plain bearings are sensitive to dust contamination affecting the sliding resistance very negatively. 
     Further, also chests of drawer may be provided with linear plain bearings, such as a simple arrangement with a groove in the drawer rack receiving a strip arranged on the drawer. Chests of drawers may also be provided with more sophisticated linear plain bearings (cf. e.g. DE 10 2011 053 946). Still, drawers getting slightly tilted often get stuck in the chest. 
     Given its simplicity, it would be desired to provide a slide member with very low sliding friction. Such a slide member may find use e.g. with wardrobe sliding doors. Further, such a slide member may find use also in other applications, such as extendable tables, kits for hanging curtains, drawers of chests of drawers, etc. 
     SUMMARY 
     Consequently, the present invention seeks to mitigate, alleviate, eliminate or circumvent one or more of the above identified deficiencies and disadvantages in the art singly or in any combination by providing a slide member, e.g. a slide bar or a sliding part, having a slide surface coated with a lacquer comprising a resin. The lacquer is in turn is at least partly coated with a lipophilic composition coating to provide a slide layer with lowered friction. This provides for a low friction slide member with efficient function in many applications, including furniture applications such as sliding doors, drawers, tables, extendable bed frames and extendable beds, etc. 
     According to one embodiment at least the slide surface of the slide member may be an aluminum surface. This provides for an efficient support for the lacquer coated on the slide surface. According to one embodiment the aluminum surface has an anodized oxide surface layer onto which the lacquer is applied. The anodized surface is hard and provides for good adhesion of the lacquer applied thereto. The slide member may be an aluminum member, e.g. aluminum profile, preferably having an anodized oxide surface layer, onto which the lacquer is applied. As an example, the slide member may be an aluminum profile having been electrophoretically, preferably anaphoretically, coated with an acrylic resin and subsequently heat cured to form the lacquer coated on the slide surface. Preferably, the aluminum profile has an anodized oxide surface layer onto which the lacquer is applied. The Honny process or one of its derivatives may be used to obtain such anodized, lacquered surfaces. Whereas the thickness of the anodized oxide surface layer preferably is at least 5 micrometers, the thickness of the lacquer coated on the slide bar may preferably be 100 micrometers or less. The lipophilic composition coating typically comprises compounds comprising C6 to C40, such as C8 to C30, non-aromatic hydrocarbyl groups, such as alkenyl groups and/or alkyl groups, e.g. alkyl groups. 
     According to another embodiment the slide surface of the slide member is made from steel, onto which the lacquer is applied. Steel is a generally strong, hard and comparably cheap material that can be used as a starting material for the slide member. Steel surfaces may be lacquered by electrocoating or autodeposition to provide a lacquer layer with uniform thickness. 
     According to a further aspect there is provided a sliding system. The system comprises the slide member according any of the above embodiments and having the form of a linear slide bar, and at least one sliding member. The interface between the slide layer of the slide bar and the sliding member forms a linear plain bearing to allow for linear movement of the sliding member along the longitudinal axis of the linear slide bar. 
     According to one embodiment the part of said sliding member to slide over the slide layer may be configured as a blade extending in the sliding direction. Further, the slide layer may be present at a track, such as in a groove or on a ridge, extending along the longitudinal axis of the slide bar. The sliding member comprises at least one individual contact point in contact with the slide bar at the interface between the slide bar and the sliding member. The contact area of each individual contact point may be less than 3 mm 2 . Further, the contact pressure in the at least one contact point may be at least 4 N/mm 2 . 
     According to a further aspect there is provided an alternative sliding system. The alternative sliding system comprises a sliding part, being a sliding member coated with a lacquer comprising a resin and also provided with a lipophilic composition thereon, the sliding part being arranged to slide along a linear slide profile to form a linear plain bearing, the sliding system further comprising at least one linear slide profile. The interface between the slide layer of the slide part and the linear slide profile forms a linear plain bearing to allow for linear movement of the slide part along the longitudinal axis of the linear slide profile. The linear slide profile may be plastic profile provided with at least one ridge extending along the longitudinal axis of the slide profile. The sliding system is arranged in a manner such that the slide layer of the slide part engages with the ridge in sliding over the linear slide profile. According to an embodiment, the plastic profile is provided with a sliding channel for the sliding part to slide in. As an example, the plastic profile may be U-shaped. Further, at least one surface of the channel, e.g. an interior surface of a U-shaped profile, may be provided with a ridge extending along the longitudinal axis of the channel. 
     According to a further aspect there is provided for use of lipophilic composition as an irreversibly bound lubricant for a slide surface of a slide member. The slide surface is coated with a lacquer comprising a resin. 
     According to a further aspect there is provided a method for providing the slide member. The method comprises the steps of:
         providing a member having a slide surface coated with a lacquer comprising a resin; and   coating at least part of the lacquer comprising a resin with a lipophilic composition to provide a slide member.       

     Further advantageous features of the invention are elaborated in embodiments disclosed herein. In addition, advantageous features of the invention are defined in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of which the invention is capable of will be apparent and elucidated from the following description of the present invention, reference being made to the accompanying drawings, in which 
         FIG.  1    depicts a cross section of a sliding system according to a first embodiment; 
         FIG.  2    depicts cross sections of the sliding member in  FIG.  1   ; 
         FIG.  3    depicts a sliding system according to a second embodiment and a cross section thereof; 
         FIG.  4    depicts a sliding member of the second embodiment in  FIG.  3   ; 
         FIGS.  5   a - c    depict a sliding part and a linear slide profile according to a third embodiment, a sliding system comprising the sliding part and the slide profile and a cross section thereof; 
         FIG.  6    depicts a schematic sliding door arrangement; 
         FIG.  7    depicts a cross section of a sliding system used for friction tests; 
         FIG.  8    illustrates an arrangement for performing friction tests with the sliding system of  FIG.  7   ; 
         FIG.  9   a    is an isometric view of a first part of a sliding system according to an embodiment for use with e.g. an extendable bed or an extendable bed frame; 
         FIG.  9   b    is a cross-sectional view of the part shown in  FIG.  9     a;    
         FIG.  10   a    is an isometric view of a second part of the sliding system according to the same embodiment; 
         FIG.  10   b    is a cross-sectional view of the part shown in  FIG.  10     a;    
         FIG.  11   a    is an isometric view of a third part of the sliding system according to the same embodiment; 
         FIG.  11   b    is a cross-sectional view of the part shown in  FIG.  11   a   ; and 
         FIG.  12    is a cross-sectional view of the extendable bed or an extendable bed frame sliding system shown in an assembled state. 
     
    
    
     DETAILED EMBODIMENTS 
     The present inventors have surprisingly found that coating a surface lacquered with a resin, for example an acrylic resin, with a lipophilic composition, such as for example sebum (natural or artificial), coconut oil, or liquid paraffin, provides a slide layer with extremely low friction (sliding resistance). The application of the lipophilic composition reduces the dynamic friction with as much as 75%. Further, and even more surprisingly, the effect is not temporarily, but seemingly permanent or at least long-lasting. The need to replenish the lubricant may hence be dispensed with. 
     In experiments employing aluminum profiles having been anaphoretically coated with an acrylic resin subsequently heat cured to form a lacquer (cf. the Honny process, initially disclosed in GB 1,126,855), wherein the lacquer of the aluminum profiles was coated with sebum, the friction remained nearly the same after more than 70,000 test cycles of a sliding door being reciprocated along the profile. So many cycles by far exceed the expected number on lifetime cycles. Further, washing the coated aluminum profile with water/detergent, ethanol, and/or iso-propanol didn&#39;t affect the friction. Without being bond to any theory, it seems that the sebum coating provides an irreversibly bound lubricant coating on top of the lacquer comprising the acrylic resin. Further, the lacquer seems to be important in providing low friction. 
     According to an embodiment there is thus provided a slide member, such as a slide bar  10 , having a slide surface  14  coated with a lacquer comprising a resin  16 . The lacquer is in turn at least partly coated with a lipophilic composition coating  18  to provide a slide layer  19  with lowered friction. By coating the lacquer, the sliding friction is not just temporarily lowered, but long term low sliding friction is obtained. As already explained the lubricating coating may be permanent, dispensing with the need to replenish the lubricating coating. Further, very low amounts of the lipophilic composition are needed to provide lowered friction. Thus, contamination of the lubricating coating does not pose any pronounced problem, as the coating, due to the very low amount present, does not have substantial adhesive properties. This is in contrast to the normal use of lubricants in plain bearings. Further, exposure to contaminations, e.g. dust etc., has been shown not to affect the lowered friction. Neither is the lubricating coating sensitive to washing. Wiping the slide member, e.g. the slide bar  10 , with a dry and/or wet cloth, does not affect the lowered friction. These properties make the slide member, e.g. the slide bar  10 , very useful for use in systems for sliding wardrobe doors, extendable tables, drawers of chests of drawers, hanging curtains, and similar applications. 
     According to an embodiment the slide member is a slide bar  10  as depicted in  FIGS.  1  to  3   . 
     Such a low amount of the lipophilic composition coating  18  is needed, that the lipophilic composition may be applied to a sliding member  20  rather than to the slide bar  10 . In sliding over the slide bar  10 , the lipophilic composition will be transferred to the slide bar  10  to provide a lipophilic composition coating  18 . Hence, the lipophilic composition coating  18  could be applied to the slide bar  10 , to the sliding member  20 , or both. 
     According to the alternative embodiment depicted in  FIGS.  5   a - c   , the slide member is a sliding part  110  whose slide layer, having a similar composition as the slide layer  19  described hereinbefore with reference to  FIG.  1   , is arranged to slide along the longitudinal axis of a linear slide profile  120 , e.g. a plastic profile, to form a linear plain bearing. At least the slide surface (similar to the slide surface  14  of  FIG.  1   ) of the sliding part  110  may, according to one embodiment, be an aluminum surface, preferably having an anodized oxide surface layer, onto which the lacquer is applied. The thickness of anodized oxide surface layer is preferably at least 5 micrometers, more preferably at least 10 micrometers. Further, the thickness of the anodized layer, if present, may be less than 250 micrometers, such as less than 100 micrometers or less than 50 micrometers. A sliding part according to such an alternative embodiment, an example of which is described in  FIGS.  5   a - c   , is less preferred for use in supporting heavy sliding doors. It is however considered to be well suited for use in sliding systems for e.g. extendable tables, drawers, etc. 
     While the slide member, e.g. a slide bar  10 , preferably is an aluminum member, e.g. a linear aluminum profile, with an aluminum oxide layer, also other materials coated with a lacquer comprising a resin may be considered. In order to allow for long term use and to carry loads, the slide member is typically made from a hard material, such as metal or glass. Especially the surface of the slide member should preferably be hard. The Vickers hardness of the material from which the slide member is made, may be at least 50 MPa, preferably at least 100 MPa, more preferably at least 150 MPa, and most preferably at least 300 MPa. According to an embodiment, the slide member is a metal member, such as an aluminum member or a steel member. In such embodiment, the member is made of a metal. While it is preferred if an aluminum member has an oxide layer, also a raw, i.e. not oxidized, lacquered aluminum member may be used. It is however preferred if the surface of the aluminum member is oxidized to provide the aluminum member with a hard oxide surface layer. 
     The slide member, e.g. a slide bar  10 , may be an aluminum member. Further, the surface of the aluminum member coated with the lacquer may be an aluminum oxide layer. The thickness of such oxide layer may be at least 5 micrometers, more preferably at least 10 micrometers. Further, the thickness of the oxide layer may be less than 250 micrometers, such as less than 100 micrometers or less than 50 micrometers. As known in the art, the durability and hardness of the surface of aluminum profiles may be improved by oxidation due to the properties of aluminum oxide. The oxide layer initially provided by anodically oxidation is porous. While the pores may be closed by steam treatment, sealing via anaphoretically coating with an acrylic resin subsequently heat cured to form the lacquer, is even more effective in sealing the porous aluminum oxide layer: This method, firstly disclosed by Honny Chemicals Co. Ltd. (cf. GB 1,126,855), is often referred to as the Honny process. 
     Further, compared to plastic slide bars, a hard, stiff bar, such as aluminum or steel bar, may accept far more heavy loads and still provide low friction. The present slide bar  10  may thus also be used for sliding drawers. 
     In addition, it has been found that a relatively high contact pressure in the contact between the slide bar  10  and the sliding member  20  reduces the friction. For this reason as well it is beneficial to make the slide bar  10  from a hard material, such as aluminum or steel, since such materials can accept higher contact pressures, thereby reducing friction. 
     According to an embodiment, the low friction slide bar  10  is a linear aluminum profile. Preferably, the linear aluminum profile is oxidized (e.g. anodized) in order to increase the hardness of the surface. The profile is typically anaphoretically coated with an acrylic resin subsequently heat cured, thereby providing a linear slide bar  10  having a lacquered slide surface  14 . The aluminum profile may be anodized to obtain an anodized layer thickness of at least 5 micrometers, more preferably at least 10 micrometers, prior to application of the resin of the lacquer. Further, thickness of the anodized layer may be less than 250 micrometers, such as less than 100 micrometers or less than 50 micrometers. Such profiles may be obtained via the Honny process (cf. above) or one of its derivatives. Typically, the Honny process is used to provide white, glossy profiles. However, neither the Honny process nor the present embodiments are limited to white profiles. The preferable feature is that the lacquer is suitable for being coated with the lipophilic composition coating  18 . 
     As known in the art, various resins, e.g. thermosetting resins, may be used to lacquer aluminum bars and other bars, i.e. to form a lacquer on aluminum bars and other bars. Further, thermosetting resins may also be used to lacquer other metal members, e.g. a sliding member made of steel. The lacquer comprises a resin. As known to the skilled person, a lacquer is a hard, thin coating. The resin of the lacquer may for this application preferably comprise polar groups, such as hydroxyl groups, carboxylic acid groups, amide groups, cyano groups (nitrile groups), halide groups, sulfide groups, carbamate group, aldehyde groups, and/or ketone groups. Further may the resin of the lacquer be a thermosetting resin. 
     Examples of resins for lacquering metal comprise acrylic resins and polyurethane resins. According to an embodiment, the resin is an acrylic resin, such as an acrylate resin, an acrylamide resin, a methacrylate resin, or a methyl methacrylate resin, and mixtures thereof. According to another embodiment, the resin is a polyurethane resin. The acrylic resin may be a thermosetting resin. 
     According to another embodiment, the resin of the lacquer is selected from the group consisting of: acrylic resins, acrylate resins, acrylamide resins, methacrylate resins, methyl methacrylate resins, acrylonitrile resins, styrene-acrylonitrile resins, acrylonitrile styrene acrylate resins, reaction products or a mechanical mixture of alkyd resin and water-soluble melamine resin, reaction products or a mechanical mixture of a vinyl-modified unsaturated alkyd resin and a water-soluble melamine resin, and polymers and mixtures of one or several of these resins. 
     Further, the thermosetting resin may the reaction product or a mechanical mixture of an alkyd resin and water-soluble melamine resin, or of a vinyl-modified unsaturated alkyd resin and a water-soluble melamine resin, the water-soluble melamine resin being obtained from hexamethylol melamine hexaalkylether. Vinyl modified unsaturated alkyd resins may be made by polymerization of a vinyl monomer with an alkyd resin composed of an unsaturated oil or fatty acid. As known to the skilled person, the term “vinyl monomer” relates to a monomer having a vinyl group (—CH═CH 2 ) in the molecule, such as an acrylic ester, for example methyl acrylate and ethyl acrylate, a methacrylic ester, for example methyl methacrylate and hydroxyethyl methacrylate, an unsaturated, organic acid, for example acrylic acid and methacrylic acid, and styrene. 
     Processes for obtaining thermosetting acrylic resins are well-known to the skilled person. As an example, they may be obtained by heating and stirring a mixture consisting of organic solvents, such as methanol, ethylene glycol, monobutyl ether, and/or cyclohexanone, unsaturated organic acids, such as acrylic acid, methacrylic acid, and/or maleic anhydride, a cross-linking vinyl monomer (as defined above), such as methylol-acrylamide and/or methylol methacrylamide, a polymerizable vinyl monomer, such as styrene and/or acrylic acid ester, polymerization catalysts, such as benzoyl peroxides and/or lauroyl peroxides, and polymerization regulators, such as dodecyl mercaptan and/or carbon tetrachloride, to carry out polymerization, thereafter neutralizing the product with, for example, an aqueous solution of ammonia and/or triethylamine to make the resin soluble in water. Further, as known to the skilled person, thermosetting resins composed of alkyd resins and water-soluble melamine resin may be obtained from hexamethylol melamine hexaalkyl ether, may be obtained by mixing a water-soluble melamine resin at a temperature of from room temperature to 100° C. with an alkyd resin modified with a fatty acid, the alkyd resin having an acid value of from 10 to 80 and being obtained by heating a mixture consisting of (1) a saturated or unsaturated aliphatic acid, (2) ethylene glycol, glycerol, polyethylene glycol, other polyhydric alcohol or an epoxide, (3) adipic acid, sebacic acid, maleic anhydride or other polybasic acid or anhydride, and (4) a small quantity of cyclohexanone, toluene or other organic solvent. Thermosetting resins may also be obtained by mixing a water-soluble melamine resin and an alkyd resin from the ester exchange process, the resin being obtained by esterifying a mixture of dehydrated castor oil, an above-mentioned polyhydric alcohol and a small amount of an ester exchanging catalyst such as caustic potash, and thereafter esterifying also an above-mentioned polybasic acid or anhydride. As further known to the skilled person, thermosetting resins consisting of a modified acrylic resin and a water-soluble melamine resin, obtained from hexamethylol melamine hexaalkyl ether, may be obtained by polymerising by heating and stirring a mixture consisting of organic solvents, such as methanol, ethylene glycol, monobutyl ether and/or cyclohexanone, unsaturated acids, such as acrylic acid and/or methacrylic acid, a vinyl monomer (as hereinabove defined), such as styrene and/or acrylic acid ester, a cross-linking vinyl monomer, if necessary, such as methylol, is normally used. Good results may be obtained by using a concentration of resin of from 5 to 20% by weight and by regulating the voltage and the initial current density within a safe and economical range. 
     As known to the skilled person further resins for use in lacquering metal surfaces are known in the art. As an example, the resin of the lacquer may be selected from the group consisting of cationic epoxy electrocoat, epoxy and polyester resins, and polyester resins. Still further, lacquers adapted for autodeposition coating, such as Autophoretic™ coatings (e.g. Aquence™ Autophoretic® 866™ and BONDERITE® M-PP930™, the latter being an epoxy-acrylic urethane) available from Henkel AG, DE, may also be used in lacquering surfaces comprising iron. 
     The slide surface  14  may be lacquered by electrocoating involving dipping the slide member into a bath containing the lacquer and applying an electric field to deposit lacquer onto the slide member acting as one of the electrodes. Further, the lacquer may be provided in powder form or in liquid form. Both powder and liquid lacquers may be sprayed onto the slide surface  14  to coat it. For powder lacquers, electro static coating may be used. For liquid lacquers a wet spray application or application in a bath may be used. Further, liquid lacquers in a bath may apart from electrocoating be applied by autodeposition. 
     In order to provide low friction, the thickness of the lacquer should be as even as possible. Thus it may be preferred to apply the lacquer by an electrocoating process, e.g. anaphoretic coating (cf. the Honny method) or cataphoretic coating, providing very even coatings. There are two types of electrocoating, i.e. anodic and cathodic electrocoating. Whereas the anodic process was the first to be developed commercially, the cathodic process is nowadays more widely used. In the anodic process, a negatively charged material is deposited on the positively charged component constituting the anode. In the cathodic process, positively charged material is deposited on the negatively charged component constituting the cathode. In the art, cathodic electrocoating is also known as cathodic dip painting (CDP), cathodic dip coating, cataphoretic coating, cataphoresis and cathodic electrodeposition. Further, the electrocoating process may also be referred to by the trade names of the bath material used. Examples include Cathoguard (BASF), CorMax (Du Pont), Powercron (PPG) and Freiotherm (PPG). Further, also electrostatically coating by powder lacquers or autodeposition in a bath provide even coatings and may thus be used. 
     In lacquering steel surfaces, autodeposition may be used. As recognized by the skilled person, one of the important steps in autodeposition is the coating bath itself, where water-based paint emulsion at low solids (usually around 4-8% by weight) is combined with two other products. A “starter” solution of acidified ferric (Fe 3+ ) fluoride initiates the coating reaction and an oxidizing product stabilizes the metal ions in the solution. The coating emulsion is stable in the presence of ferric ions, but unstable in the presence of ferrous ions (Fe 2+ ). Therefore, if ferrous ions are liberated from the metal substrate, localized paint deposition will occur on the surface Immersion of a component made from ferrous metal (e.g. steel) into an autodeposition bath causes the acidic environment to liberate ferrous ions, thereby causing the coating emulsion to be deposited, forming a mono-layer of paint particles. Henkel Adhesive Technologies (US)//Henkel AG &amp; Co. KGaA (Germany) provides coatings under the trademark BONDERITE® for use in autodeposition. 
     As the lacquer coated on the slide member, e.g. the slide bar  10 , typically is more compressible than the material of the slide member, e.g. the slide bar  10 , itself, and as load carrying sliding members will apply pressure on the lacquer in sliding over the slide bar  10 , the thickness of the lacquer preferably is to be kept thin to reduce compression of it. Compressing the lacquer may negatively affect the sliding resistance; especially at the start of the sliding sequence, i.e. when the sliding member starts to move along the slide bar  10  from a previous state of being at rest. 
     According to an embodiment, the thickness of the lacquer coated on the slide member, e.g. the slide bar  10 , is thus 100 μm or less, preferably 75 μm or less, more preferably 50 μm or less. Further, the thickness of the lacquer coated on the slide member, e.g. the slide bar  10 , may be 5 to 75 μm, such as 10 to 50 μm, or 15 to 40 μm. Layers of these thicknesses have been found to provide for efficient sliding behavior, also at the instance when the sliding member starts to move along the slide bar  10 . 
     Not only the low dynamic friction provided by the present slide member, but also the low difference between the static and dynamic friction provided by the present slide member is beneficial in terms of the sliding behavior. 
     In order to reduce the friction of the slide member, e.g. the slide bar  10 , the slide member, e.g. the slide bar  10 , is, at least partly, coated with a lipophilic composition coating  18  to provide a slide layer  19 . Further, while various components may be present in the lipophilic composition coating  18  present on the lacquer, the composition typically comprises components with intermediate to long carbon chains, e.g. carbon chains having a carbon atom length of C6 or more, such as C8 or more. Thus, the lipophilic composition coating  18  may comprise compounds comprising C6 to C40, such as C8 to C30 or even C10 to C24, non-aromatic hydrocarbyl groups. Typical examples of such non-aromatic hydrocarbyl groups are alkenyl groups and alkyl groups, e.g. alkyl groups. Examples of compounds comprising such non-aromatic hydrocarbyl groups are:
         C6 to C40 non-aromatic hydrocarbons, such as alkenes and/or alkanes, e.g. alkanes;   tri-glycerides, e.g. triglycerides comprising C6 to C40, such as C8 to C30, non-aromatic hydrocarbyl groups; and   fatty acids, e.g. C6 to C40, such as C8 to C30, carboxylic acids, and esters thereof, such as alkyl esters of fatty acids, e.g. methyl esters.       

     As known to the skilled person and as recognized in IUPAC&#39;s gold book (International Union of Pure and Applied Chemistry, Compendium of Chemical Terminology—Gold Book, Version 2.3.3 of 2014 Feb. 24):
         hydrocarbon denotes compounds consisting of carbon and hydrogen only;   hydrocarbyl denotes univalent groups formed by removing a hydrogen atom from a hydrocarbon;   alkane denotes acyclic branched or unbranched hydrocarbons having the general formula C n H 2n+2 ;   alkene denotes acyclic branched or unbranched hydrocarbons having one or more carbon-carbon double bond(s);   alkyl denotes a univalent group derived from alkanes by removal of a hydrogen atom from any carbon atom —C n H 2n+1 ;   alkenyl denotes an univalent group derived from alkenes by removal of a hydrogen atom from any carbon atom;   fatty acid denotes an aliphatic monocarboxylic acid;   triglyceride denotes an ester of glycerol (propane-1,2,3-triol) with three fatty acids (tri-O-acylglycerol); and   non-aromatic denotes a compound not comprising any cyclically conjugated molecular entity with increased stability due to delocalization.       

     According to an embodiment, the lipophilic composition coating  18  present on the lacquer comprises at least 1 wt. % such as at least 5 wt. %, 10 wt. %, 25 wt. %, 50 wt. %, 60 wt. %, 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. % or at least 90 wt. % of compounds comprising C6 to C40, such as C8 to C30, alkyl groups. Thus, the lipophilic composition coating  18  may comprise least 1 wt. % such as at least 5 wt. %, 10 wt. %, 25 wt. %, 50 wt. %, 60 wt. %, 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. % or at least 90 wt. % C6 to C40, such as C8 to C30, alkenes and/or alkanes, e.g. alkanes. Further, the lipophilic composition coating  18  present on the lacquer may comprise least 1 wt. % such as at least 5 wt. %, 10 wt. %, 25 wt. %, 50 wt. %, 60 wt. %, 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. % or at least 90 wt. % triglycerides and/or fatty acids (or alkyl esters thereof). 
     Whereas fatty acids have been found to improve the lubricating effect of mixtures of alkanes, such as liquid paraffin, they are less effective if used on their own. It is thus preferred if the lipophilic composition present on the lacquer is not only composed of fatty acids. The lipophilic composition present on the lacquer may thus comprise less than 99 wt. % fatty acids, such as less than 95 wt. % fatty acids. However, lipophilic compositions essentially only comprising triglycerides, such as coco nut oil, provide very low friction and do thus represent a preferred lipophilic composition present on the lacquer. 
     According to an embodiment, the lipophilic composition coating  18  present on the lacquer comprises at least 1 wt. % such as at least 5 wt. %, 10 wt. %, 25 wt. %, 50 wt. %, 60 wt. %, 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. % or at least 90 wt. % of alkenes and/or alkanes, e.g. alkanes and 0.1 to 50 wt. %, such as 1 to 40 wt. % or 5 to 30 wt. % triglycerides and/or fatty acids 
     According to another embodiment, the lipophilic composition coating  18  present on the lacquer comprises at least 1 wt. % such as at least 5 wt. %, 10 wt. %, 25 wt. %, 50 wt. %, 60 wt. %, 75 wt. %, 80 wt. % or at least 90 wt. % in total of triglycerides and/or fatty acids and 0.1 to 95 wt. %, such as 1 to 90 wt. % or 5 to 60 wt. % alkenes and/or alkanes, e.g. alkanes. 
     As already mentioned, typical examples of compounds comprising C6 to C40 non-aromatic hydrocarbyl groups are tri-glycerides and fatty acids. According to an embodiment, the lipophilic composition coating  18  present on the lacquer comprises triglycerides and/or fatty acids. The lipophilic composition coating  18  may thus comprise more than 25 wt. %, e.g. more than 50 wt. %, such as 50 to 100 wt. %, or 75 to 95 wt. %, in total of triglycerides and fatty acids. The triglycerides and/or fatty acids may either be used as the major component in the lipophilic composition coating  18  or as additives. 
     If to be used as a major component, the lipophilic composition present on the lacquer coating may comprise more than 50 wt. %, such as 50 to 100 wt. %, or 75 to 95 wt. %, triglycerides, e.g. triglycerides to at least 90%. wt composed of a glycerol residue and 3 residues of caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and/or arachidic acid, such as 3 residues of lauric acid, myristic acid, palmitic acid, and/or stearic acid. According to an embodiment, the lipophilic composition coating  18  present on the lacquer comprises coconut oil, such as at least 25 wt. % such as at least 50 wt. %, 60 wt. %, 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. % or at least 90 wt. % coconut oil. Coconut oil comprises triglycerides composed of fatty acids that are to a high degree saturated fatty acids. The coconut oil may be hydrogenated to various degrees to further reduce the amount of unsaturated fatty acids residues. Further, the lipophilic composition coating  18  present on the lacquer may comprise more than 50 wt. %, such as 50 to 100 wt. %, or 75 to 95 wt. % fatty acids, e.g. caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and/or arachidic acid, such as lauric acid, myristic acid, palmitic acid, and/or stearic acid. Furthermore, the lipophilic composition coating  18  present on the lacquer may comprise more than 50 wt. %, such as 50 to 100 wt. %, or 75 to 95 wt. % alkyl esters of fatty acids, e.g. methyl or ethyl esters. The esterified fatty acids may be caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and/or arachidic acid, such as lauric acid, myristic acid, palmitic acid, and/or stearic acid. 
     If to be used as an additive, the lipophilic composition coating  18  present on the lacquer may comprise 0.1 to 50 wt. %, such as 1 to 30 wt. % or 5 to 15 wt. %, triglycerides, e.g. triglycerides to at least 90% composed of a glycerol residue and 3 residues of caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and/or arachidic acid, such as 3 residues of lauric acid, myristic acid, palmitic acid, and/or stearic acid. A preferred example of composition to be used to provide a lipophilic composition coating  18  comprising triglycerides is coconut oil. According to an embodiment, the lipophilic composition coating  18  present on the lacquer comprises coconut oil, such as 0.1 to 50 wt. %, such as 1 to 30 wt. % or 5 to 15 wt. %, coconut oil. According to an embodiment, the lipophilic composition coating  18  present on the lacquer comprises at least 50 wt. % coconut oil, such as at least 60 wt. %, 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. %, or at least 90 wt. % coconut oil. Coconut oil comprises triglycerides composed of fatty acids that are to a high degree saturated fatty acids. The coconut oil may be hydrogenated to various degrees to further reduce the amount of unsaturated fatty acids residues. Further, the lipophilic composition present on the lacquer may comprise 0.1 to 50 wt. %, such as 1 to 30 wt. % or 5 to 15 wt. %, of fatty acids, e.g. caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and/or arachidic acid, such as lauric acid, myristic acid, palmitic acid, and/or stearic acid. Furthermore, the lipophilic composition coating  18  present on the lacquer may comprise 0.1 to 50 wt. %, such as 1 to 30 wt. % or 5 to 15 wt. %, of alkyl esters of fatty acids, e.g. methyl or ethyl esters. The esterified fatty acids may be caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and/or arachidic acid, such as lauric acid, myristic acid, palmitic acid, and/or stearic acid. 
     Both saturated and un-saturated compounds comprising C6 to C40 non-aromatic hydrocarbyl groups are well-known in the art. While both types of compounds will be efficient in reducing the sliding resistance, saturated compounds comprising C6 to C40 non-aromatic hydrocarbyl groups are deemed to be less sensitive to oxidative degradation. Thus, it may be preferred to use compounds comprising C6 to C40 non-aromatic hydrocarbyl groups being triglycerides composed of saturated fatty acids residues and/or saturated fatty acids in the composition. It may however not be necessary to use a 100% saturated fatty acids and/or triglycerides. As example, coconut oil is envisaged to have sufficient long term stability, though saturated fatty acids and/or triglycerides are preferred in terms of their long term stability. 
     As mentioned, the lipophilic composition coating  18  present on the lacquer may comprises at least 1 wt. % C6 to C40 alkanes. As an example, the lipophilic composition coating  18  present on the lacquer may thus comprise mineral oil, such as at least 1 wt. %, such as at least 5 wt. %, 10 wt. %, 25 wt. %, 50 wt. %, 60 wt. %, 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. %, or at least 90 wt. % mineral oil. Mineral oil is a colorless, odorless, light mixture of higher alkanes from a non-vegetable (mineral) source. Further, the lipophilic composition present on the lacquer coating may comprise liquid paraffin, such as at least 1 wt. %, such as at least 5 wt. %, 10 wt. %, 25 wt. %, 50 wt. %, 60 wt. %, 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. %, or at least 90 wt. % liquid paraffin. Liquid paraffin, also known as paraffinum liquidum, is a very highly refined mineral oil used in cosmetics and for medical purposes. A preferred form is the one having CAS number 8012-95-1. Furthermore, the lipophilic composition coating  18  present on the lacquer may comprise petroleum jelly (also known as petrolatum, white petrolatum, soft paraffin or multi-hydrocarbon), such as at least 1 wt. %, such as at least 5 wt. %, 10 wt. %, 25 wt. %, 50 wt. %, 60 wt. %, 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. %, or at least 90 wt. % petroleum jelly. Petroleum jelly is a semi-solid mixture of hydrocarbons (with carbon numbers mainly higher than 25). A preferred form is the one having CAS number 8009-03-8. 
     A further embodiment (cf.  FIGS.  1  and  3   ) of the invention relates to sliding system  1 , comprising the disclosed slide bar  10  and at least one sliding member  20 . The slide bar  10  is typically linear, such as linear aluminium profile. By arranging the interface between slide layer  19  of the slide bar  10  and the sliding member  20  in sliding contact a linear plain bearing is provided. The sliding member  20  is arranged to allow for linear movement of the sliding member in sliding over the slide layer  19  along the longitudinal axis of the linear slide bar  10 . Further, the slide bar  10  may be provided with a track, which in this embodiment has the form of a groove  11  extending along the longitudinal axis off the slide bar  1  and defining a slide direction along the longitudinal axis of the slide bar  10 . When the slide bar  10  is provided with a groove  11 , the slide layer  19  is present at least in the groove  11 . 
     The track, which may for example have the form of a groove, an example of such a groove  11  is illustrated in  FIG.  1   , or the form of a ridge, improves the control of the lateral position of the sliding member  20  in relation to the slide bar  10  when the sliding member  20  slides along the slide bar  10 . 
     An enlarged detail in  FIG.  1    illustrates how the slide member  10 , which is made from, in this embodiment, aluminum, has a slide surface  14 . The slide surface  14  is coated with the lacquer comprising a resin  16 . The lacquer comprising a resin  16  is in turn coated with a lipophilic composition coating  18 . Thereby a slide layer  19  is formed. The sliding member  20  may slide over this slide layer  19  at a very low friction. 
     Further, as shown in  FIGS.  2  and  4   , the part of the sliding member  20  arranged in contact with the slide layer  19  may be configured as a blade  21  extending in the sliding direction. It was surprisingly found that decreasing the contact area at the interface between the slide bar  10  and the sliding member  20  reduced the friction. Normally the risk for the bearing seizing typically increases with reduced contact area. In order to provide the sliding system  1 , the sliding member  20  comprises at least one contact point in contact with the slide bar  10  at the interface between the slide bar  10  and the sliding member  20 . According to an embodiment, the contact area of each individual contact point is less than 3 mm 2 , such as less than 1.5 mm 2 , or less than 0.75 mm 2 . The slide member may further be provided with more than one contact point, such as 2, 3, or 4 contact points. If, for example, the sliding member is provided with a blade  21  extending in the sliding direction, then the edge of the blade  21  represents an individual contact point. 
     It has been found that the friction becomes lower when the contact pressure between the sliding member and the slide bar is relatively high. The contact pressure is calculated by dividing the load carried by each individual contact point by the contact area of the contact point. For example, if the sliding door has a total weight of 8.5 kg this represents a total load of 83.3 N. The sliding door may carried by two sliding members  20  of the design illustrated in  FIG.  2   . Each sliding member  20  having four contact points, i.e. edges of the blades  21 ,  22 ,  23  in  FIG.  2   , each such contact point having an area of 0.675 mm 2 . The contact pressure is then: 83.3 N/(2×4×0.675 mm 2 )=15.4 N/mm 2 . Preferably, the contact pressure in said at least one contact point is at least 4 N/mm 2 , more preferably at least 8 N/mm 2 , such as at least 12 N/mm 2 . Preferably, the contact pressure is lower than the strain at yield (=yield strength) for the material from which the sliding member  20  is made. 
     In order to provide low friction, at least the part of the sliding member  20  in contact with the slide layer  19  is preferably made of a plastic comprising a polymer, such as a polymer comprising polar groups. Examples of such polar groups include hydroxyl groups, carboxylic acid groups, amide groups, halide groups, sulfide groups, cyano groups (nitrile groups), carbamate groups, aldehyde groups, and/or ketone groups 
     The polymer may be selected from the group consisting of polyoxymethylenes (POM), polyesters (e.g. thermoplastic polyesters, such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polylactic acid (PLA), as well as bio-based thermoplastic polyesters, such as polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB), and polyethylene furanoate (PEF)), polyamides (PA), polyvinyl chloride (PVC), polyphenylene sulfide (PPS), polyaryletherketone (PAEK; e.g. Polyether ether ketone (PEEK)), and Polytetrafluoroethylene (PTFE). Further, not only the part of the sliding member  20  in contact with the slide layer  19  may be made of a polymer, but the entire sliding member  20 . Thus, sliding member may be made from a plastic comprising a polymer. As recognized by the skilled person, the plastic may further comprise other additives, such as fillers, colorants, and/or plasticizers. Further, the sliding member  20  may be made from a composite comprising a polymer, such as one of the above listed polymers, filled with particles and/or fibers. The particles and/or fibers will increase the hardness, the stiffness, the creep resistance and elongation (compression) at yield of the sliding member  20 . While not affecting the friction, presence of particles and/or fibers may affect the wear. Thus, use of particles and/or fibers in the plastic is less preferred. 
     According to an embodiment (cf.  FIG.  2   ) the sliding member  20  may be provided with two parallel, displaced blades  21 ,  22  in order to prevent rotation along the sliding axis. Further, the slide bar  10  may be provided with two parallel grooves  11 ,  12  arranged along each side of its longitudinal sliding axis. Parallel grooves  11 ,  12  will support and guide such two parallel blades  21 ,  22  of the sliding member (cf.  FIG.  1   ). Further, slide bars with two parallel grooves  11 ,  11 , supporting two separate slide members  20 , are preferred in sliding systems arranged to support more than one sliding door (cf.  FIG.  3   ) as only one slide bar is then required. Furthermore, the sliding member  20  may be provided with two, or more, parallel blades  21 ,  23  (cf.  FIGS.  2  and  4   ) arranged along the same longitudinal axis. The sliding member  20  may be provided with two parallel blades  21 ,  23  adapted for running in the same groove  11  independently of the presence, or non-presence, of parallel, displaced blades  21 ,  22  adapted for running in two parallel grooves  11 ,  12 . 
     The sliding system  1  may be used to support a sliding door  30  connected to the sliding member  20 . Thus, the sliding member  20  may be provided with fastening arrangements  28 , e.g. holes, pins, etc., for connecting the sliding member  20  to the sliding door  30 . 
     A further embodiment (cf.  FIG.  5   ) of the invention relates to alternative sliding system  1 , comprising a linear slide profile  120  and a slide member, the slide member being a sliding part  110  arranged to slide along the longitudinal axis of a linear slide profile  120  to form a linear plain bearing. The interface between the slide layer (similar to the slide layer  19  illustrated in  FIG.  1   ) of the sliding part  110  and the linear slide profile forms a linear plain bearing to allow for linear movement of the sliding part  110  sliding along the longitudinal axis of the linear slide profile  120 . According to such an embodiment, the linear slide profile  120  may be a plastic profile provided with at least one ridge  121   a - e  extending along the longitudinal axis of the profile. The plastic profile may be provided with a sliding channel  125  for the sliding part  110  to slide in. At least one surface of the channel  125  may be provided with a ridge  121   a - e  extending along the longitudinal axis of the channel  125 . As an example, the plastic profile  120  may be U-shaped with at least one of its interior surfaces provided with a ridge extending along the longitudinal axis of the slide bar. The plastic profile  120  may be fitted inside a support member  150 , such as a metal rod, to enhance the mechanical strength of the plastic profile. Further, also other surfaces of the channel  125  may be provided with ridge(s)  121   a - e  extending along the longitudinal axis of the channel. More than one interior side of a U-shaped plastic profile may be provided with a ridge(s)  121   a - e  extending along the longitudinal axis of the profile  120 . The sliding system is arranged in manner such that the slide layer  19  of the sliding part  110  engages with the ridge(s)  121   a - e  in sliding over the linear slide profile  120 . Part of the sliding part  110  may be arranged to fit into the sliding channel  125  and to engage with the ridge(s)  121   a - e  in sliding within the channel (cf.  FIG.  5   c   ). This part may have a cross-section corresponding, in general shape, not size, to the cross-section of the channel excluding the ridge(s)  121   a - e . The plastic profile and its ridge(s)  121   a - e  may then serve to guide the sliding part  110 . 
     As already mentioned, it was surprisingly found that decreasing the contact area at the interface between the two parts of the linear bearing reduces the friction. Normally one would expect the friction to increase with reduced contact area. Further, the risk for the bearing seizing typically increases with reduced contact area. In order to provide the sliding system, the linear slide profile  120  comprises at least one contact point in contact with the sliding part  110  at the interface between the linear slide profile  120  and the sliding part  110 . According to an embodiment, the contact area of each individual contact point is less than 3 mm 2 , such as less than 1.5 mm 2 , or less than 0.75 mm 2 . The linear slide profile  120  may further be provided with more than one contact point, such as 2, 3, or 4 contact points. If the linear slide profile is provided with a ridge  121   a - e  extending in the sliding direction, its edge, or rather that part of the edge which is at a certain instance in contact with the sliding part, represents the contact point. 
     It has been found that the friction becomes lower when the contact pressure between the sliding part  110  and the linear slide profile bar  120  is relatively high. The contact pressure is calculated by dividing the load carried by each individual contact point by the contact area of the contact point. Preferably, the contact pressure in said at least one contact point is at least 4 N/mm 2 , more preferably at least 8 N/mm 2 , such as at least 12 N/mm 2 . Preferably, the contact pressure is lower than the strain at yield (=yield strength) for the material from which the linear slide profile  120  is made. 
     In order to provide low friction, at least the part of the linear slide profile  120  in contact with the slide layer  19  of the sliding part  110  is preferably made of a plastic comprising a polymer, such as a polymer comprising polar groups. Examples of such polar groups include hydroxyl groups, carboxylic acid groups, amide groups, halide groups, sulfide groups, cyano groups (nitrile groups), carbamate groups, aldehyde groups, and/or ketone groups 
     The polymer may be selected from the group consisting of polyoxymethylenes (POM), polyesters (e.g. thermoplastic polyesters, such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polylactic acid (PLA), as well as bio-based thermoplastic polyesters, such as polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB), and polyethylene furanoate (PEF)), polyamides (PA), polyvinyl chloride (PVC), polyphenylene sulfide (PPS), polyaryletherketone (PAEK; e.g. Polyether ether ketone (PEEK)), and Polytetrafluoroethylene (PTFE). According to one embodiment not only the part of the linear slide profile  120  in contact with the slide layer  19  is made of a polymer, but the entire linear slide profile  120  is made of a polymer. Thus, linear slide profile  120  may in its entirety be made from a plastic comprising a polymer. As recognized by the skilled person, the plastic may further comprise other additives, such fillers, colorants, and/or plasticizers. Further, the linear slide profile  120  may made from a composite comprising a polymer, such as one of the above listed polymers, filled with particles and/or fibers. The particles and/or fibers will increase the hardness, the stiffness, the creep resistance and elongation (compression) at yield of the linear slide profile. While not affecting the friction, presence of particles and/or fibers may still affect the wear. Thus, use of particles and/or fibers in the plastic is less preferred. A further embodiment of the invention relates to a sliding door arrangement  2 , schematically depicted in  FIG.  6   , such as a sliding door arrangement for a wardrobe. Such an arrangement  2  comprises the disclosed sliding system  1  and a sliding door  30 . One, or often two or three, sliding member/-s  20  is/are arranged to support the sliding door  30  to allow for linear movement of the sliding door  30  along the longitudinal axis of the linear slide bar  10 . Typically the sliding door  30  is connected to the sliding member  20  supporting the door. The slide bar  10  may be horizontally arranged in use with the slide layer  19  facing upwards to support the sliding member  20 . As the sliding member  20  may be arranged to horizontally slide over the slide bar  10 , the sliding door  30  may be moved along the horizontal axis of the linear slide bar  1 . The sliding door, such as a sliding door  30  for a wardrobe, will typically be arranged hanging from the linear slide bar  10 . 
     A sliding door  30  may however also be mounted standing on the linear slide bar  10 . Smaller doors, such as kitchen cabinet doors, are examples of doors which may be standing on the linear slide bar  10 . Further, sliding doors  30  mounted standing on the linear slide bar  10 , may not necessarily extend in the vertical plane, but may be slightly tilted with respect to the vertical plane, as is known for kitchen cabinet doors. However, given the low friction provided by the present sliding system, also larger doors may be mounted standing on the linear slide bar  10 . 
     Furthermore there is, according to an embodiment, provided a method for providing slide member. In such a method there is provided a member having a slide surface  14  coated with a lacquer comprising a resin  16 . In order to provide the member with lowered friction, the lacquer is, at least partly, coated with a lipophilic composition coating  18 . Aspects of the member, the lacquer, and the lipophilic composition coating  18  have been provided herein above and are applicable to this embodiment as well. In applying the lipophilic composition to provide the lipophilic composition coating  18 , the lipophilic composition may firstly be heated, such as melted, to reduce its viscosity. Further, the lipophilic composition may be dissolved in a solvent to facilitate application. Lipophilic composition being in a liquid state at room temperature may also be applied directly. After application, any such solvent may be evaporated, at least partly. The lipophilic composition to provide the lipophilic composition coating  18  may be applied in various ways, such as by spraying, smearing, painting, coating, spreading etc. 
     According to an embodiment, the lipophilic composition is applied by the end-consumer. Thus, the slide member, the sliding system or arrangements comprising the slide member may be provided together with a lipophilic composition to be applied by the end-consumer, i.e. the lacquer is un-coated upon delivery. 
     Similarly, another embodiment relates to the use of such a lipophilic composition as an irreversibly bound lubricant for a slide surface  14  of a slide member. By “irreversibly bound lubricant” is, according to an embodiment, meant that the lubricant is not removed from the slide surface  14  during normal operation of the sliding system and that it cannot be easily removed using mechanical means, e.g. it cannot be removed by wiping the slide surface  14  with a cloth. As described herein, the slide surface of the slide member is coated with a lacquer comprising a resin  16 . Aspects of the member, the lacquer, and the lipophilic composition coating  18  have been provided herein above and are applicable to this embodiment as well. 
     As described previously a sliding system according to the principles set forth in this specification may also be used for extendable beds, extendable bed frames, sofa beds, drawers, tables, etc. An embodiment of an extendable bed/bed frame sliding system  1001  for an extendable bed or bed frame is shown in  FIGS.  9   a   - 12 , whereby the individual parts are disclosed in detail. The sliding system  1001  allows for a full extension of a moving part of an extendable bed or extendable bed frame, meaning that the moveable part may be drawn out from a fixed frame structure. The moveable part may e.g. be a foot end of the extendable bed or extendable bed frame, while the fixed frame structure may be the head end. 
     The sliding system  1001  comprises a first guiding rail  1100 , which is best shown in  FIGS.  9   a - 9   b   , comprising securing means  1120 , here in the form of two spaced apart through holes, for securely attaching the first guiding rail  1100  to the inner wall of a fixed frame structure, such as to the head end of the extendable bed or bed frame. Horizontal mounting of the first guiding rail  1100  is preferred. The first guiding rail  1100  has a C-shape, better shown in  FIG.  9   b   , and is provided with two or more sets of sliding members  1200  that are all mounted inside the C-shape of the guiding rail  1100 . Two sliding members  1200  are fixedly mounted to the upper part of the C-shape, and two sliding members  1200  are fixedly mounted to the bottom part of the C-shape. The sliding members  1200  are arranged in pairs, such that an upper sliding member  1200  and a lower sliding member  1200  are aligned in a vertical direction. The sliding members  1200  are thus stationary relative the fixed frame structure when the first guiding rail  1100  is mounted to the fixed frame structure. The sliding members  1200  may be made of polymer materials according to the principles described hereinbefore. 
     Now turning to  FIGS.  10   a - b    the sliding system  1001  also comprises a slide member which in this embodiment is an intermediate guiding rail in the form of an intermediate slide bar  1300 . The intermediate slide bar  1300  is configured as a C-shape and has an upper and outer slide surface  1320 , an upper and inner slide surface  1340 , a bottom and inner slide surface  1360 , and a bottom and outer slide surface  1380 , as best shown in  FIG.  10   b   . These slide surfaces  1320 ,  1340 ,  1360 ,  1380  are preferably planar, and the width of the outer slide surfaces  1320 ,  1380  is dimensioned to engage with the sliding members  1200  of the first guiding rail  1100 . The slide surfaces  1320 ,  1230 ,  1360 ,  1380  may be formed according to the principles described hereinbefore, similar to the slide surface  14 , and are provided with a lacquer comprising a resin and a lipophilic composition coating to form respective slide layers which may be similar to the slide layer  19  described hereinbefore, see for example  FIG.  1    and the related description. 
     The intermediate slide bar  1300  is thus configured to be received by the C-shaped first guiding rail  1100 . 
     The sliding system  1001  also comprises a second guiding rail  1400  to be fixedly mounted to a moveable part, e.g. the foot end, of the extendable bed or extendable bed frame. The second guiding rail  1400  is provided with means (not shown), such as screw holes or similar, for attaching the second guiding rail  1400  to the moveable part. As can be seen in  FIGS.  11   a - b    the second guiding rail  1400  is L-shaped, whereby the lower part  1420  can be used for aligning with the bottom end of the moveable part. Hence the moveable part of the extendable bed or bed frame may rest on the lower part  1420 , while the side wall of the moveable part is screwed to the vertical part  1440  of the second guiding rail  1400 . 
     The second guiding rail  1400  is provided with one or more sliding members  1500  protruding outwards for engagement with the inner slide surfaces  1340 ,  1360  of the intermediate slide bar  1300 . In this embodiment there are two separate sliding members  1500  attached to the vertical part  1440  of each second guiding rail  1400 . The vertical height of the sliding members  1500  thus corresponds to the distance between the two inner slide surfaces  1340 ,  1360  of the intermediate slide bar  1300 . The sliding members  1500  may be made of polymer materials according to the principles described hereinbefore. 
       FIG.  12    illustrates a cross-sectional view of the sliding system  1001  in an assembled state. Two sliding interfaces are thus provided, the first one being realized by the sliding engagement between the sliding members  1200  of the first guiding rail  1100  and the outer slide surfaces  1320 ,  1380  of the intermediate slide bar  1300 . The second sliding interface is realized by the sliding engagement between the inner slide surfaces  1340 ,  1360  of the intermediate slide bar  1300  and the sliding members  1500  of the second guiding rail  1400 . The sliding interfaces may include protrusions, e.g., blades, and grooves according to principles described hereinabove, see for example  FIG.  1   . 
     While the embodiment of  FIGS.  9   a    to  12  is described as an extendable bed and/or extendable bed frame sliding system  1001  for an extendable bed or extendable bed frame it will be appreciated that the slide member and the sliding system  1001  according to the described principles may be useful also in other applications, in particular applications where a moveable part is to be drawn out from a fixed part, including e.g. extendable tables, drawers to be drawn out of chests of drawers, etc. 
     Without further elaboration, it is believed that one skilled in the art may, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative and not limitative of the disclosure in any way whatsoever. 
     Although the present invention has been described above with reference to specific embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims and other embodiments than those specifically described above are equally possible within the scope of these appended claims, e.g. different embodiments than those described above. 
     In the claims, the term “comprises/comprising” does not exclude the presence of other elements or steps. Additionally, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion of two features in different claims does not imply that a combination of those features is not feasible and/or advantageous. 
     In addition, singular references do not exclude a plurality. The terms “a”, “an”, “first”, “second” etc. do not preclude a plurality. 
     EXAMPLES 
     The following examples are mere examples and should by no means be interpreted to limit the scope of the invention, as the invention is limited only by the accompanying claims. 
     General 
     All chemicals were obtained from Sigma-Aldrich. In providing mixtures, e.g. palmitic acid 10 mass % in liquid paraffin, the two compounds (e.g. 3 g palmitic acid and 27 g liquid paraffin) were mixed under heating to melt the mixture. Further, the mixtures were applied to the slide bar before solidifying. 
     The test procedure used was based on SS-EN 14882:205. In short, a sled with parallel plastic blades (four in total; two along each longitudinal slide axis) of POM was positioned on an anodized aluminum profile (cf.  FIG.  7   ) having been anaphoretically coated with an acrylic resin and subsequently heat cured to provide a lacquered slide surface. Aluminum profiles lacquered in this way are for example provided by Sapa Profiler AB, 574 38 Vetlanda, Sweden, and are marketed under the trade name SAPA HM-white, the materials being produced using the Sapa HM-white method which is based on the above referenced Honny method. In the friction measurements, the sled was pulled over the slide bar at a constant speed of 500 mm/min and the force necessary to pull the sled was registered using an Instron 5966 tension testing system (cf.  FIG.  8   ). The total weight of the sled corresponds to 10 N. Fresh profiles were used for each lipophilic composition, as the lipophilic compositions cannot be removed once applied. However, the profiles were re-used after the control experiments (no lipophilic compositions applied), washing and ageing, respectively. 
     Example 1 
     By using the test procedure described above, the resulting friction from application of various lipophilic compositions to anodized, lacquered aluminum profiles was determined. The resulting dynamic friction, mean value from three test sequences, was registered and compared to the dynamic friction for anodized aluminum profiles provided with a lacquer but not coated with any lipophilic composition (=control). The results are provided in Table 1 and 2 below. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Fatty acids in liquid paraffin 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Lipophilic 
                   
                   
                 Dynamic friction 
               
               
                   
                 composition 
                 Wash 
                 Ageing 
                 Mean (n = 3) 
               
               
                   
                   
               
               
                   
                 No (control) 
                 — 
                 — 
                 0.214 
               
               
                   
                 MA5% 
                 — 
                 — 
                 0.049 
               
               
                   
                 MA10% 
                 — 
                 3 days 
                 0.046 
               
               
                   
                 MA30% 
                 — 
                 — 
                 0.049 
               
               
                   
                 MA10% 
                 Yes 
                 — 
                 0.041 
               
               
                   
                 PA10% 
                 — 
                 3 days 
                 0.047 
               
               
                   
                 PA10% 
                 Yes 
                 — 
                 0.042 
               
               
                   
                 SA10% 
                 — 
                 3 days 
                 0.050 
               
               
                   
                 SA10% 
                 Yes 
                 — 
                 0.044 
               
               
                   
                 LP 
                 — 
                 — 
                 0.053 
               
               
                   
                 LP 
                 Yes 
                 — 
                 0.050 
               
               
                   
                   
               
               
                   
                 MA5%/10%/30% = Myristic acid 5/10/30 mass % in liquid paraffin 
               
               
                   
                 PA10% = Palmitic acid 10 mass % in liquid paraffin 
               
               
                   
                 SA10% = Stearic acid 10 mass % in liquid paraffin 
               
               
                   
                 LP = Liquid paraffin 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Triglycerides in liquid paraffin 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Lipophilic 
                   
                   
                 Dynamic friction 
               
               
                   
                 composition 
                 Wash 
                 Ageing 
                 Mean (n = 3) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 No (control) 
                 — 
                 — 
                 0.214 
               
               
                   
                 TM10% 
                 — 
                 — 
                 0.0510 
               
               
                   
                 TM10% 
                 Yes 
                 — 
                 0.0524 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 TP10% 
                 — 
                 3 
                 days 
                 0.0454 
               
               
                   
                 TP10% 
                 — 
                 6 
                 weeks 
                 0.0513 
               
            
           
           
               
               
               
               
               
            
               
                   
                 TP10% 
                 Yes 
                 — 
                 0.0440 
               
               
                   
                 TS10% 
                 — 
                 — 
                 0.0524 
               
               
                   
                 TS10% 
                 Yes 
                 — 
                 0.0504 
               
               
                   
                 LP 
                 — 
                 — 
                 0.053 
               
               
                   
                 LP 
                 Yes 
                 — 
                 0.050 
               
               
                   
                   
               
               
                   
                 TM10% = Trimyristate 10 mass % in Liquid paraffin 
               
               
                   
                 TP10% = Tripalmitate 10 mass % in Liquid paraffin 
               
               
                   
                 TS10% = Tristearate 10 mass % in Liquid paraffin 
               
               
                   
                 LP = Liquid paraffin 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Fatty acids in liquid paraffin 
               
            
           
           
               
               
               
               
            
               
                   
                 Lipophilic 
                   
                 Dynamic friction 
               
               
                   
                 composition 
                 Wash 
                 Mean (n = 3) 
               
               
                   
                   
               
               
                   
                 LP 
                 — 
                 0.054 
               
               
                   
                 LP 
                 Yes 
                 0.042 
               
               
                   
                 LA10% 
                 — 
                 0.058 
               
               
                   
                 LA 10% 
                 Yes 
                 0.041 
               
               
                   
                 LA 30% 
                 — 
                 0.046 
               
               
                   
                 LA 30% 
                 Yes 
                 0.039 
               
               
                   
                 LA 50% 
                 — 
                 0.048 
               
               
                   
                 LA 50% 
                 Yes 
                 0.036 
               
               
                   
                 LA 70% 
                 — 
                 0.041 
               
               
                   
                 LA 70% 
                 Yes 
                 0.036 
               
               
                   
                 Coconut oil 
                 — 
                 0.033 
               
               
                   
                 Coconut oil 
                 Yes 
                 0.037 
               
               
                   
                   
               
               
                   
                 LA10/30/50/70% = Lauric acid 10/30/50/70 mass % in Liquid paraffin 
               
            
           
         
       
     
     As can be seen from Table 1 and 2, the resulting dynamic friction was reduced by about 75% by applying a lipophilic compositions to the anodized aluminum profiles, though the initial dynamic friction of the un-coated anodized aluminum profiles was not that high. Furthermore, whereas the dynamic friction remained low and nearly the same for the coated profiles over repeated cycles, the dynamic friction for un-coated anodized aluminum profiles was significantly increased (seizing) already after less than 20 test cycles. 
     It can also be seen from the above tables  1  and  2  that the tests including fatty acids or triglycerides resulted in a somewhat lower friction compared to pure Liquid paraffin, in particular when the fatty acid is myristic acid or palmitic acid, and when the triglyceride is tripalmitate. Coconut oil, being a mixture of various triglycerides, in which lauric acid is the most common fatty acid residue, provided very low friction (cf. Table 3). Further, neither ageing nor washing (wiping by a wet cloth 6 times, followed by wiping 4 times with a dry cloth) had any significant effect on the dynamic friction. 
     Example 2 
     By using the test procedure described above, the resulting friction at various loads (5, 10 and 20 N, respectively) using liquid paraffin as the lipophilic composition coating was determined. Increasing the load did not result in increased friction. On the contrary, the lowest load (5 N) displayed the highest friction (friction value 0.052 (at 5 N) vs. friction values 0.045 (at 10 N)/0.046 (at 20 N)). 
     Example 3 
     In an additional experiment, a corresponding aluminum bar, but without any lacquer, was used. Use of palmitic acid 10 mass % in liquid paraffin as lubricant on the non-lacquered bar resulted in a dynamic friction of 0.1132, i.e. more than 100% higher than corresponding dynamic friction obtained with the lacquered aluminum bar (cf. Table 1; 0.042 and 0.047, respectively). 
     Example 4 
     In additional examples also steel profiles as well as other lacquers were evaluated. 
     Lacquers: Teknotherm 4400 (Teknos)—wet spray lacquer, Standofleet® (Standox) wet spray lacquer, Powercron® 6200HE (PPG)—cationic epoxy electrocoat, Interpon AF (AkzoNobel)—powder coating, and Alesta (Axalta)—powder coating. 
     Profiles: Aluminium (Al), and steel (Fe) 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Coconut oil on aluminum and steel profiles 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Dynamic friction 
                   
                 Dynamic friction 
               
               
                 Lacquer 
                 Profile 
                 Mean (n = 3) 
                 Profile 
                 Mean (n = 3) 
               
               
                   
               
               
                 Teknotherm 
                 Al 
                 0.040 
                 Fe 
                 0.050 
               
               
                 Standofleet 
                 Al 
                 0.045 
                 Fe 
                 0.048 
               
               
                 Interpon AF 
                 Al 
                 0.024 
                 Fe 
                 0.034 
               
               
                 Powercron 
                 Al 
                 0.021 
                 Fe 
                 0.041 
               
               
                 Alesta 
                 Al 
                 0.025 
                 Fe 
                 0.038 
               
               
                   
               
            
           
         
       
     
     As can be seen from Table 4, the aluminum profiles displayed lower friction than the steel profiles though also the steel profiles displayed a very low friction. Further, whereas some of the alternative lacquers displayed comparable or lower friction than the SAPA HM-white profiles (dynamic friction mean: 0.033), the wet lacquered profiles displayed slightly higher friction. Without being bond to any theory, this may be due to wet lacquered profiles inherently having somewhat thicker lacquer and/or varying thickness of the lacquer. Further, in comparing coconut oil and liquid paraffin (data not shown) it was seen that coconut oil generally provided somewhat lower friction. 
     Example 5 
     Tests were also performed in a full-scale test rig using a wardrobe door with a weight of 8.5 kg and using two sliding members  20  and a slide bar  10  of the type described hereinabove with reference to  FIG.  1   . When applying a lipophilic composition coating comprising 100% Liquid paraffin to the lacquer of the slide bar  10  the wardrobe door could still be moved back and forth without problems and at still a low friction after 500 000 cycles of reciprocation of the wardrobe door. In a comparative test the same equipment was used, but without any lipophilic composition coating being applied on the lacquer. In the latter case the tests had to be stopped already after less than 30 cycles as the test equipment was about to break down due to rapidly increasing friction between the sliding members and the slide bar (seizing).