Formulation for a blade element of a windscreen wiper blade

Abstract

A formulation for the preparation of a wiping blade element for a vehicle windscreen wiper blade is disclosed. The formulation has an elastomer material based on chloroprene rubber in which plasticizing additives are incorporated, where the plasticizing additives include a combination of at least a first additive, the pour point of which is less than 50 C., and at least a second additive, the pour point of which is greater than 50 C. The first additive is octyl sebacate in a proportion of 4 phr and the second is a naphthalic oil plasticizer or a C.sub.18-C.sub.30 tricarboxylic ester in a proportion of 10 phr.

Claims

1. A formulation for the preparation of a wiping blade element for a vehicle windscreen wiper blade, the formulation comprising: an elastomer material based on chloroprene rubber in which plasticizing additives are incorporated, wherein the plasticizing additives comprise a combination of at least a first additive, the pour point of which is less than 50 C., and at least a second additive, the pour point of which is greater than 50 C.

2. The formulation according to claim 1, in which the pour point of the first additive is greater than or equal to 60 C.

3. The formulation according to claim 2, in which the first additive comprises a C.sub.18-C.sub.30 dicarboxylic ester.

4. The formulation according to claim 1, in which the pour point of the second additive is less than or equal to 30 C.

5. The formulation according to claim 1, in which the pour point of the second additive is one selected from a group consisting of between 40 C. and 30 C.

6. The formulation according to claim 5, in which the second additive is a naphthalic oil plasticizer or a C.sub.18-C.sub.30 tricarboxylic ester.

7. The formulation according to claim 1, in which the amount of the first additive is between 3 and 5 phr (parts by hundred parts of rubber, by weight).

8. The formulation according to claim 7, in which the amount is 4 phr (pans by hundred parts of rubber, by weight).

9. The formulation for the preparation of a wiping blade element according to claim 1, in which the ratio by weight of the first additive to the second additive is between 2 and 3.

10. The formulation according to claim 9, in which the ratio is equal to 15.

11. A wiping blade element for a vehicle windscreen wiper blade prepared from a formulation according to claim 1.

12. A vehicle windscreen wiper blade comprising a wiping blade element according to claim 11.

13. A process for the manufacture of a wiping blade element for a vehicle windscreen wiper blade by vulcanization of a formulation according to claim 1.

14. The process according to claim 13, comprising a stage of moulding the wiping blade element.

15. The formulation of claim 3, wherein the C.sub.18-C.sub.30 dicarboxylic ester is octyl sebacate.

Description

(1) In a specific embodiment, the said first additive comprises an ester and more preferably a C.sub.18-C.sub.30 dicarboxylic ester, for example octyl sebacate.

(2) Preferably, the pour point of said second additive is less than or equal to 30 C.

(3) More preferably, the pour point of the said second additive is between 46 C. and 30 C., preferably between 40 C. and 30 C. and more preferably substantially equal to 30 C.

(4) In a specific embodiment, the said second additive is a naphthalic oil plasticizer or a C.sub.18-C.sub.30 tricarboxylic ester.

(5) Advantageously, the amount of the first additive is between 3 and 5 phr (parts per hundred parts of rubber, by weight) and more advantageously it is 4 phr.

(6) Preferably, the ratio by weight of the first additive to the second additive is between 2 and 3 and more preferably is substantially equal to 2.5.

(7) The invention also relates to a wiping blade element for a vehicle windscreen wiper blade prepared from a formulation as described above and to a vehicle windscreen wiper blade comprising such a wiping blade element.

(8) Finally, it relates to a process for the manufacture of a wiping blade element for a vehicle windscreen wiper blade by vulcanization of a formulation as described above.

(9) According to one embodiment of the invention, the above process comprises a stage of moulding the wiping blade element.

(10) A better understanding of the invention will be obtained and other aims, details, characteristics and advantages of the invention will become more clearly apparent during the detailed explanatory description which will follow of an embodiment of the invention given as purely illustrative and nonlimiting example.

(11) In order to increase the value of the tangent of the mixture, the Applicant Company provides for the addition of a plasticizer having a high pour point which is of the order of 50 to 30 C. and in any case greater than 50 C. The pour point of a viscoelastic material corresponds to the temperature from which it begins to leave the solid phase and to flow. The plasticizer added can be a product such as those known under the trade name Nyflex 230P or TOTM, the pour points of which are respectively 30 C. and 46 C., or more generally a product of the naphthalic oil plasticizer type or else a tricarboxylic ester in the range from C.sub.18 to C.sub.30. The addition of this plasticizer increases the tangent at 20 C. and consequently the viscoelastic damping of the elastomer in the frequency range of 600 to 1000 Hz.

(12) On the other hand, this addition exhibits the disadvantage of damaging the properties of resistance to cold of the rubber. The Applicant Company consequently provides for the addition to the elastomer mixture of a second plasticizer having a low pour point. This second plasticizer is of the ester type and makes it possible, as a result of its high molecular mobility, to improve the low-temperature elasticity of the material. The pour point recommended by the invention is set as being less than 50 C. By way of example, it is possible to choose an ester of the octyl sebacate (or DOS) type, the pour point of which is 55 C., or more generally a dicarboxylic ester in the C.sub.18 to C.sub.30 range.

(13) The recommended contents for the two plasticizers are 4 phr for the plasticizer having a low pour point and 10 phr for the plasticizer having a high pour point. Tests have shown that the addition of a plasticizer having a high pour point at a concentration of 10 phr, in combination with a reduction to 4 phr in that having a low pour point, provides an improvement in the tangent at 20 C. of 0.2 or even 0.3 point, for both products mentioned above, with respect to a formulation which comprises only the single plasticizer having a low pour point. Furthermore, it is found that the greatest gain (0.3 versus 0.2 point) is contributed by the plasticizer which has the highest pour point (30 C. versus 46 C., in the case in point, in both experimental formulations).

(14) The value of tangent obtained at 20 C. with these additives thus reaches values, respectively, of 0.7 and 0.8 (versus 0.4 and 0.6 respectively without additive having a high pour point) during an experiment in forced vibrations of 30 microns in amplitude under a frequency of 1 Hz. These values guarantee an absence of vexatious noise for a wiping blade element in use on a windscreen.