WO2013004449A2

WO2013004449A2 - An elongated element with a thermoplastic coating

Info

Publication number: WO2013004449A2
Application number: PCT/EP2012/060896
Authority: WO
Inventors: Alain Leplae; Marcelo XAVIER; Filip Verhoeve
Original assignee: Nv Bekaert Sa
Priority date: 2011-07-07
Filing date: 2012-06-08
Publication date: 2013-01-10
Also published as: WO2013004449A3

Abstract

An elongated element comprises a core element, wherein the core element is coated with an outer layer, and the outer layer comprises a thermoplastic and a nucleating agent, the nucleating agent is 2% to 30% in weight in outer layer. The outer layer provides low friction coefficient and dull surface to the elongated element.

Description

An elongated element with a thermoplastic coating

Description

Technical Field

[0001 ] The present invention relates to an elongated element coated with an

outer layer. The present invention further relates to the use of the coated elongated element. The present invention also relates to a wiper blade and a guide wire comprising the coated elongated element.

Background Art

[0002] As a reinforcing element, a steel wire or strip has several applications, such as reinforcing wiper blade, functioning as guide wire, integrating in a tissue or reinforcing a foam.

[0003] Wiper blades are most frequently used in vehicles to remove

condensations such as rain or snow off windshields. A wiper blade comprises two parts mainly, one is wire or strip as reinforcement and another is rubber blade as wiping element. The existing technology is applying on the wire or strip lubricants such as oil or graphite, with an optimization design on the profile or with a special film of polymer before being embedded into the rubber blade. While embedding the existing wire or strip into the rubber blade, the production speed is low, and it causes a high energy loss and environment pollution. Additionally, the sliding property of the wiper blade is not so good, and the wiping capabilities are not good enough.

[0004] DE 10025629 discloses a wiper blade that a polymer coating is applied on the surface of the wire or strip. To this wiper blade, the production speed is low, the production cost is too high and the wiping property is still not so good.

[0005] There is another problem of the existing wiper blade, the existing wiper blade scatters the sunlight, and this will affect driver's sight while driving. It makes the driving unsafe.

[0006] While applying the wire for integration in a tissue or for reinforcement of a foam, the contact between the introducing wire and the tissue or foam makes a noise, and the noise causes an uncomfortable feeling. [0007] It is required to find a wire or strip to avoid the above problems.

Disclosure of Invention

[0008] An object of the present invention is to solve the problems of the prior art.

[0009] Another object of the present invention is to provide an elongated element as a reinforcing element.

[0010] A further object of the present invention is to provide a guide wire

comprising an elongated element.

[001 1 ] Another object of the present invention is to provide a wiper blade

comprising an elongated element.

[0012] According to the present invention, an elongated element is provided. The elongated element comprises a core element, wherein the core element is coated with one outer layer, the outer layer comprises a thermoplastic and a nucleating agent, wherein the nucleating agent is 2% to 30% in weight in the outer layer.

[0013] While applying the invention elongated element for reinforcing a wiper blade, the production speed of wiper blade is improved, and the energy loss and environment pollution are reduced. Further, the sliding property and the wiping capabilities of the wiper blade are also improved.

Additionally the scattering of sunlight is avoided and the safety of driving is hence improved.

[0014] While applying the invention elongated element for integration in a tissue or for reinforcement of a foam, the friction and hence the noise caused by the contact of the elongated element and the tissue or foam is reduced or avoided.

[0015] By adding the nucleating agent into the thermoplastic, the thermoplastic is nucleated or recrystallized, as a result a fine crystallization structure of the thermoplastic is obtained. The outer layer with the fine crystallization structure provides a dull surface and low friction coefficient to the elongated element. The outer layer comprising thermoplastic and nucleating agent with dull surface and low friction coefficient solves the problems of the prior art, i.e. low production speed, high energy loss and environment pollution, low sliding property and the wiping capabilities of a wiper blade. [0016] The friction coefficient is quite reduced in the present invention compared with the prior art, even the friction coefficient can be even reduced to be 30% of the values of the prior art.

[0017] The dull surface here means that the surface has a low gloss value. The gloss value is less than 30 units determined by using a reflectometer geometry of 60° as specified in ISO method 2813. The gloss value is even less than 20 units.

[0018] In the present invention, the nucleating agent is a kind of chemical

substance which helps to promote the nucleation or crystallization of the thermoplastic. It can be any one of the nucleating agents known in the art. According to the present invention, the nucleating agent is incorporated in plastics form for the growth of crystals in the thermoplastic melt. In polypropylene, for example, a higher degree of crystallinity and more uniform crystalline structure is obtained by adding a nucleating agent such as adipic and benzoic acid or certain of their metal salts.

[0019] The nucleating agent may be an inorganic substance or an organic

substance. The nucleating agent may be selected from talcum, metal oxides such as magnesium oxide, carbonate, phosphates, sulphates, alkaline earth metals, mono- or poly- carboxylic acids and the salts thereof, adipic acid, sodium succinate, sodium benzoate or polymeric compounds such as ionic copolymers (ionomers). The preferable embodiments of nucleating agent are sugar acetals (Millad(R) family from Milliken

Chemical, Spartanburg, USA), hyper nucleating agents, such as, for instance, the calcium salt of 1 ,2-cyclohexane dicarboxylic acid (available as Hyperform(R) HPN-20E from Milliken Chemical) and the disodium salt of bicyclo[2.2.1 ]heptane-2,3-dicarboxylic acid (available as Hyperform(R) HPN-68 from Milliken Chemical, Spartanburg, USA) and organophosphate derivatives, such as ADKSTAB(R) NA-1 1 (available from ADEKA, Japan; main component: sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate), ADKSTAB(R) NA-21 (available from ADEKA, Japan; main component: aluminium-hydroxy-bis [2, 2'-methylene-bis (4, 6-di- te/f- butylphenyl) phosphate]) and ADKSTAB(R) NA-71 (available from ADEKA, Japan; main component: Lithium 2, 2'-methylene-bis (4,6-di-te/f- butylphenyl) phosphate), and/or Ciba(R) IRGASTAB(R) NA 287 (a proprietary high efficiency nucleating agent available from Ciba AG, Basel, Switzerland). Other nucleating agents of particular interest to the present invention include beta -nucleating agents for PP such as, for instance, NJSTAR(R) TF1 (available from New Japan Chemical, Japan) as well as TNB-5 (a cyclohexyl terephthalamide derivative). Yet another nucleating agent of interest to the present invention is the clarifying agent

RIKACLEAR(R) PC1 (distributed by Rika, UK), equal to NJSTAR(R) PC-1 (produced by New Japan Chemical, Japan).

[0020] Preferably the nucleating agent is 10% to 20% in weight in the outer layer.

The more the nucleating agent, the lower the gloss value.

[0021 ] US2005/0004295 discloses a coating for reducing friction coefficient, the coating comprises talc. The method of producing the coating is first preparing a aqueous solution by adding the water to the talc dropwise, then spraying the solution to the wiper, and finally drying the solution. The talc is held or dispersed in the solution. To ensure the holding or dispersion of the talc, some additives are added into the solution, i.e.

wetting agent, binder of the solution (such as resin), waterproofing, thickness agent. All these additives are for the holding or dispersion of the talc in the solution. On the final product with the coating, after drying, the particles of talc are bound to each other by the resin, however, the resin does not fill in all the interstices between the particles of talc, thus to form cavities of the coating which confer a hydrophilic character and contribute an improved quality of the wiping. The talc and the resin are independent of each other, in other words, the talc won't influence the resin and it won't change the chemical and physical properties of the resin, the purpose of the resin is only to hold the particles of talc and provide a strength. This is not a nucleation or recrystallization and is different from the present invention. In the present invention, the thermoplastic is nucleated by the nucleating agent. The nucleating agent is to promote the nucleation or crystallization of the thermoplastic, the nucleating agent is incorporated with the thermoplastic by a chemical bonding force like hydrogen bond, such a bonding help to promote the nucleation or cystallization of the thermoplastic, as a result the thermoplastic will have a fine crystallization structure and improved properities. [0022] According to the present invention, the thickness of the outer layer comprising thermoplastic and nucleating agent is preferably between

10μΐη and 250μηη, more preferably between 15μηη and Ι ΟΟμηη.

[0023] According to the present invention, a thermoplastic in outer layer can be any one of the existing thermoplastic known by the people in the field. Preferably thermoplastic is selected from polyethylene, polyurethane, polypropylene, polystyrene, polyethylene terephthalate, polyethylene napthalate, polybuteen terephthalate polyvinylchloride, polyamide, polyester, polyimide, polycarbonate, styrene acrilonitryl, acrylonitril- butadiene-styrene, thermoplastic polyurethane, thermoplastic polyolefins, thermoplastic copolyetheresters, or copolymers of these polymers.

[0024] To the present invention, the elongated element is an element having

elongation, it can be a wire, blade, strip, sheet or cord. The core element can be a plurality of element like a wire, blade, strip, sheet or cord. The material of the core element can be metal, metal alloy or glass. Preferably the core element is a steel wire or a glass wire. A steel wire means a steel filament with any kind of cross-section and with any diameter. Preferably the steel wire is a round steel wire, a flat steel wire or a steel strip. Also a profiled wire can be considered. For the purpose of this invention, a cord is defined as a structure composed of two or more filaments or a

combination of strands or filaments and strands, while a strand is defined as a group of filaments combined together to form a unit product for further processing.

[0025] Additionally a corrosion resistance layer can be applied between the core element and the outer layer comprising thermoplastic and nucleating agent. The corrosion resistance layer helps to reduce the corrosion, i.e. the corrosion from the water or acid.

[0026] The corrosion resistance layer can be any one of the anticorrosion coating known by the people in the art. Some prior arts disclose a lot about the corrosion resistance layer such as WO201 1058021 , US 2010266872 and US 5342699. Preferably the corrosion resistance layer is a zinc or a zinc alloy coating like zinc-aluminum coating, zinc brass coating or zinc aluminum magnesium coating while the elongated element is made of metal. Such coating can prevent the corrosion of the core element from the water or acid while it can also improve the adhesion between the core element and the outer layer comprising thermoplastic and nucleating agent.

[0027] To make the outer layer stable, besides a thermoplastic and a nucleating agent, the outer layer further comprises some other additives, such as a polymeric impact modifier and/or a stabilizer. The modifier and stabilizer help to obtain a higher impact resistance, a duller surface and a stabler coating. The other additives can be waxes, fillers and teflon powders.

[0028] A coloring pigment also can be added into the outer layer comprising

thermoplastic and nucleating agent, either inorganic or organic pigment. Also the pigment can be special pigment such as luminescent pigment. The elongated element can be applied to be with the whole visible spectrum, from violet to red.

[0029] The elongated element according to the present invention can be used as a reinforcing element for a plurality of industrial applications. Preferably the elongated element can be applied to reinforce push pull cable, power spring, wiper blade, guide wire, tissue or foam.

[0030] According to an aspect of the present invention, a guide wire is provided.

The guide wire comprises an elongated element and a thermoplastic layer covering the elongated element. The elongated element comprises a core element which is coated with one outer layer, the outer layer comprises a thermoplastic and a nucleating agent, wherein the nucleating agent is 2% to 30% in weight in the outer layer.

[0031 ] According to another aspect of the present invention, a wiper blade is provided. The wiper blade comprises an elongated element and rubber blade. The elongated element comprises a core element being coated with one outer layer, the outer layer comprises a thermoplastic and a nucleating agent, wherein the nucleating agent is 2% to 30% in weight in the outer layer.

[0032] The structure of the wiper blade can be any one of the existing wire blade known by the people in the art such as the wiper blade described in US201 1088192 or US2005044651 . [0033] For a wiper blade, the outer layer comprising thermoplastic and nucleating agent provides an improved production speed, a good sliding property and an assurance of safe driving to the wiper blade.

Brief Description of Figures in the Drawings

[0034] Figure 1 shows a cross-sectional view of an invention steel strip.

[0035] Figure 2 shows a cross-sectional view of an invention steel strip.

[0036] Figure 3 shows a cross-sectional view of an invention steel cord.

[0037] Figure 4 shows a cross-sectional view of a wiper blade.

Mode(s) for Carrying Out the Invention

[0038] In the present invention, the elongated element comprises a core element and an outer layer upon the core element. The core element here can be a steel wire or strip, steel cord or glass wire.

[0039] An elongated steel core is manufactured as follows:

[0040] The wire rod composition has preferably a carbon content ranging

between a minimum carbon content of 0.25% and a maximum carbon content of about 1 .10%, more preferably a carbon content ranging between a minimum content of 0.60% and a maximum content of about 1 .10%, a manganese content ranging from 0.40% to 0.70%, a silicon content ranging from 0.15% to 0.30%, a maximum sulphur content of 0.03%, a maximum phosphorus content of 0.30%, all percentages being weight percentage wherein the total weight is the weight of wire rod.

Usually there are only traces of copper, nickel, aluminium, titanium, and nitrogen and / or chromium, except for very high tensile strengths.

[0041 ] The wire rod is firstly cleaned by mechanical descaling and / or by

chemical pickling in a H₂SO₄ or HCI solution in order to remove the oxides present on the surface. The wire rod is then rinsed in water and is dried. The dried wire rod is then subjected to a first series of dry drawing operations in order to reduce the diameter until a first intermediate diameter. [0042] At this first intermediate diameter, e.g. at about 3.0 to 4.5 mm, the dry drawn steel wire is subjected to a first intermediate heat treatment, called patenting. The steel wire is then ready for further mechanical deformation.

[0043] Thereafter the steel wire is further dry drawn from the first intermediate diameter until a second intermediate diameter in a second number of diameter reduction steps. The second diameter typically ranges from 1 .0 mm to 3.5 mm.

[0044] At this second intermediate diameter, the steel wire is subjected to a

second patenting treatment to allow for transformation to pearlite.

[0045] Additionally, after this second patenting treatment, the steel wire can be provided with a zinc coating or zinc alloy coating.

[0046] Then steel wire (with or without additional zinc or zinc alloy coating) is subjected to a final series of cross-section reductions by means of wet drawing machines to obtain the pre-determined diameter. A round steel wire is obtained.

[0047] Possibly the steel wire is oil tempered steel wire.

[0048] Possibly one round steel wire goes through one or more adapted forming profile dies to obtain a flat steel wire or other profiled wire, such as oval profiled, rectangular profile, I -profiled, or H-profiled wire. The flat steel wire is also called a steel strip.

[0049] Possibly several steel wires, round and/or flat steel wires, go through the twisting machine to get a steel cord.

[0050] A steel wire or strip or a steel cord is obtained by the above processes to be the core element. Besides these, the core element can also be a glass wire.

[0051 ] The outer layer coated elongated element is obtained by the following process:

1 ) preparing an elongated core element;

2) preparing a coating solution by dissolving the nucleating agent into the thermoplastic bath;

3) applying the coating solution of thermoplastic comprising nucleating agent upon the elongated core element by extruding.

In the step 2), first, melting the thermoplastic to provide a thermoplastic bath, and then dissolving the nucleating agent into the thermoplastic bath under a high temperature, finally cooling down the whole solution, thus obtaining a coating solution. During the cooling down of the whole solution, the nucleation or crystallization of thermoplastic is occurred.

[0052] Preferably, the nucleating agent is inorganic substance or organic

substance. The nucleating agent is preferably selected from talcum, metal oxides such as magnesium oxide, carbonate, phosphates, sulphates, alkaline earth metals, mono- or poly- carboxylic acids and the salts thereof, adipic acid, sodium succinate, sodium benzoate or polymeric compounds such as ionic copolymers (ionomers).

[0053] Preferably thermoplastic is selected from the group consisting of

polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyethylene napthalate, polybuteen terephthalate polyvinylchloride, polyamide, polyester, polyimide, polycarbonate, styrene acrilonitryl, acrylonitril-butadiene-styrene, thermoplastic polyurethane, thermoplastic polyolefins, thermoplastic copolyetheresters, or copolymers of these polymers.

[0054] A pigment can be added into nucleating agent or thermoplastic or their mixture.

[0055] Figure 1 illustrates a first embodiment of an invention steel strip. The steel strip 10 has a core strip 12 and an outer layer 14. The content of the nucleating agent in the outer layer 14 is 15% in weight. The thermoplastic in the outer layer is polyethylene terephthalate (PET), the nucleating agent is phosphate.

[0056] Figure 2 illustrates a second embodiment of an invention steel strip. The steel strip 18 has a core strip 20, a corrosion resistance layer 22 and an outer layer 24. The thermoplastic in the outer layer 24 is polyethylene terephthalate (PET), the nucleating agent is a phosphate. The content of the nucleating agent in the outer layer 24 is 10.2% in weight. The

corrosion resistance layer 22 is a zinc-aluminum coating.

[0057] Figure 3 illustrate a third embodiment of invention steel cord. The steel cord 40 has a core cord 42 consisting of three steel wires 46 and an outer layer 44. The thermoplastic in the outer layer 44 is polyethylene, the nucleating agent is sodium benzoate. The content of the nucleating agent in the outer layer 44 is 23.6% in weight.

[0058] Test

A comparison test on friction coefficient is carried out. Both the static friction coefficient and dynamic friction coefficient are tested.

[0059] The test for dynamic friction coefficient is: first, sticking a rubber to a steel support with a hook on it, wherein a dynamometer is mounted on the hook; second, placing the steel support with the rubber side on the flat wire which is fixed on a second support, third, pulling the dynamometer and as soon the part begins to slide, and then obtaining the dynamic friction force on the dynamo meter. The dynamic coefficient of friction _d is determined from the average of the dynamic friction force.

[0060] The test for static friction coefficient is: first, fixing a wire on a support

which is adjustable in angle between 0 and 90°C; second, sticking a rubber part on the steel support; third, lifting the support and as soon the support with the rubber starts to slide: record the angle and obtain a static friction force F_s. Once the static force F_s is determined, the static

coefficient of friction μ₈ can be derived.

[0061 ] Steel strip 10 and two prior art steel strips which are coated with

polyethylene terephthalate (PET) or dull PET are tested. Here dull PET is a PET with dull surface. The following table 1 summarizes the test result.

[0062] Table 1

[0063] According to the test result in table 1 , it is obvious that both the dynamic coefficient and static coefficient of the invention are quite lower than the prior arts. The outer layer comprising thermoplastic and nucleating agent contributes a lot for the reduction of friction coefficient on the surface of the steel strip 10. [0064] A comparison test on surface roughness is carried out. Steel strip 10 and two prior art steel strips which are coated with polyethylene terephthalate (PET) or dull PET are tested. The test is carried out according to two direction including longitudinal direction and transverse direction. The longitudinal direction is a direction along the length of the steel strip, and transverse direction is a direction being transversal to the length of the steel strip. R_a, Rt, and R_z are tested, R_a means arithmetic average of absolute value, R_t means maximum peak height, and R_z means average distance between the highest peak and lowest valley in each sampling length. The following table 2 summarizes the test result.

[0065] Table 2

[0066] From table 2, the outer layer of PET with nucleating agent has the highest roughness, especially the highest R_a. It means that the contact surface of the coated steel strip 10 is lowest while contacting the coated steel strip with other product, and thus the steel strip 10 has the lowest friction. The highest roughness also proves that the friction coefficient of the outer layer is lowest.

[0067] A comparison test on surface gloss value is carried out. Steel strip 10 and two prior art steel strips which are coated with polyethylene terephthalate (PET) or dull PET are tested. The test is carried out according to upper side and under side. The test is also tested the type of aged and nonaged. Here 'aged' means thermally aging 30 minutes under a temperature of 140°C. The gloss value is determined by using a reflectometer geometry of 60° as specified in ISO method 2813. The following table 3 summarizes the test result. [0068] Table 3

[0069] From table 3, the surface of layer with PET and nucleating agent has

lowest gloss value which is even half lower than the gloss value dull PET which has also a dull surface. Even under the situation of aging, the gloss value of the invention wire is still quite lower than it of the existing products. In other words, the invention wire is quite suitable for the downstream production.

[0070] According the above tests, the outer layer comprising thermoplastic and nucleating agent reduces the friction coefficient of the surface of the elongated element greatly and provides a duller surface to the elongated element. The lower friction coefficient and the duller surface give advantages to the downstream production. For example, in the

downstream production of a wiper blade, the lower friction coefficient of steel strip or wire helps to improve the production efficiency, improve the production speed and lower the energy cost, and reduce the environment pollution; and the dull surface helps to avoid the scattering of sunlight and conduct to a safer driving.

[0071 ] The elongated element with an outer layer comprising thermoplastic and nucleating agent is suitable for reinforcing push pull cable, power spring, wiper blade, guide wire, tissue or foam.

[0072] For the application of reinforcing tissue or foam, the noise between the elongated element, i.e. a wire or strip, and the tissue or foam is reduced.

[0073] Figure 4 illustrates a wiper blade. The wiper blade 30 has two steel strips 12 and two springs 36, 38. Besides steel strips and springs, the remains is rubber blade. The outer layer comprising thermoplastic and nucleating agent on the steel strips 12 reduces the friction between the steel strips and rubber blade, and this conducts an improved production speed and good wiping property of the wiper blade. The outer layer also gives a dull surface to the steel strips which conducts a safer driving.

A fourth embodiment is a glass wire with an outer layer comprising polyethylene and sodium benzoate while the content of sodium benzoate is 21 % in weight in the outer layer.

Claims

1 . An elongated element comprising a core element, said core element being coated with an outer layer, said outer layer comprises a thermoplastic and a nucleating agent, characterized in that said nucleating agent is 2% to 30% in weight in said outer layer.

2. An elongated element as claimed in claim 1 , characterized in that said

nucleating agent is 10% to 20% in weight in said outer layer.

3. An elongated element as claimed in any one of claims 1 to 2, characterized in that the thickness of said outer layer is between 10 μηη and 250 μηη.

4. An elongated element as claimed in any one of claims 1 to 3, characterized in that said thermoplastic is selected from polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyethylene napthalate, polybuteen terephthalate polyvinylchloride, polyamide, polyester, polyimide,

polycarbonate, styrene acrilonitryl, acrylonitril-butadiene-styrene, thermoplastic polyurethane, thermoplastic polyolefins, thermoplastic copolyetheresters, or copolymers of these polymers.

5. An elongated element as claimed in any one of claims 1 to 4, characterized in that said nucleating agent is selected from talcum, metal oxides, phosphates, carbonates, sulphates, alkaline earth metals, organic compounds, polymeric compounds or beta nucleating agent.

6. An elongated element as claimed in any one of claims 1 to 5, characterized in that the surface of said outer layer is a dull surface with a gloss value being less than 30 units.

7. An elongated element as claimed in any one of claims 1 to 6, characterized in that said core element is made of the material selected from metal, metal alloy or glass.

8. An elongated element as claimed in any one of claims 1 to 7, characterized in that said core element is a wire, blade, strip, sheet or cord.

9. An elongated element as claimed in any one of claims 1 to 8, characterized in that a corrosion resistance layer is applied between said core element and said outer layer.

10. An elongated element as claimed in claim 9, characterized in that said

corrosion resistance layer is a zinc or zinc alloy coating.

1 1 . An elongated element as claimed in any one of claims 1 to 10, characterized in that said outer layer further comprises polymeric impact modifier and/or stabilizer.

12. A use of an elongated element as claimed in any one of claims 1 to 1 1 is as a reinforcing element.

13. A use of an elongated element as claimed in claim 12 is as a reinforcing

element for reinforcing tissue or foam.

14. A guide wire comprising an elongated element and a thermoplastic layer

covering said elongated element, said elongated element comprising a core element, said core element being coated with an outer layer, said outer layer comprising a thermoplastic and a nucleating agent, characterized in that said nucleating agent is 2% to 30% in weight in said outer layer.

15. A wiper blade comprising an elongated element and rubber blade, said

elongated element comprising a core element, said core element being coated with an outer layer, said outer layer comprising a thermoplastic and a nucleating agent, characterized in that said nucleating agent is 2% to 30% in weight in said outer layer.