Sealing composition for repairing tyres

Abstract

Sealing composition for repairing tires comprising: 15 to 80% of natural latex, 5 to 50% of synthetic latex, 10 to 60% of a glycol selected from ethylene glycol and propylene glycol and 0.05 to 5% of a mineral chosen from a phyllosilicate and silica having an average granulometric distribution in the range between 5 and 95 nm.

Claims

1. A sealing composition for repairing tyres consisting of in percentages by weight based on the total weight of the listed components: from 15% to 80% of natural latex; from 5 to 50% synthetic latex; from 10 to 60% of a glycol selected from the group consisting of propylene glycol and ethylene glycol; and optionally an additive selected from the group consisting of an anti-oxidant agent, a stabilising agent and mixtures thereof; and 0.4-0.7% silica.

2. The composition according to claim 1, wherein said silica has an average granulometric distribution in the range between 5 and 95 nm.

3. The sealing composition according to claim 1, wherein said silica has an average granulometric distribution in the range between 10 and 30 nm.

4. The sealing composition according to claim 1, wherein the diameter of the particles of said synthetic latex has an average granulometric distribution in the range between 0.05 and 0.3 m.

5. The sealing composition according to claim 4, wherein said diameter of the particles of said synthetic latex has an average granulometric distribution of 0.1 m.

6. The sealing composition according to claim 1, wherein said natural latex is present in an amount in the range between 40 and 70%.

7. The sealing composition according to claim 1, wherein said synthetic latex is present in an amount in the range between 10 and 20%.

8. The sealing composition according to claim 1, wherein said glycol is present in an amount in the range between 20 and 50%.

9. The sealing composition according to claim 1, consisting of: 30-35% of natural latex; 32-37% of synthetic latex; 25-31% of propylene glycol; 0.4-0.7% of silica having a granulometric distribution in the range between 10 and 30 nm.

10. The sealing composition according to claim 1, wherein said natural latex is a natural deproteinised latex.

11. The sealing composition according to claim 1, wherein said synthetic latex is selected from the group consisting of a styrene-butadiene and carboxylated styrene-butadiene latex.

12. The sealing composition according to claim 1, wherein said glycol is propylene glycol.

13. The sealing composition according to claim 1, wherein the synthetic latex includes polyurethane latex in an amount of 0.5 to 10% by weight based on total weight of the composition.

14. The sealing composition according to claim 1, wherein the synthetic latex includes polyurethane latex in an amount of 1% to 4% by weight based on total weight of the composition.

15. The sealing composition according to claim 1, wherein said antioxidant is present in an amount in the range of between 1% and 2.5 and said stabilizing agent is present in an amount in the [sic]range of between 0.5 and 4%.

16. The sealing composition according to claim 1, wherein said synthetic latex has a gelatinisation rate of at least 25% measured according to a mechanical stability test of the Mallon type based on JIS-K6387.

17. The sealing composition according to claim 16, wherein said synthetic latex has a gelatinisation rate higher than 50% measured according to a mechanical stability test of the Mallon type based on JIS-K6387.

18. The sealing composition according to claim 1, wherein the synthetic latex includes a polyurethane latex.

Description

BEST MODE FOR CARRYING OUT THE INVENTION

(1) Phyllosilicates are silicates characterised by a layered structure with tetrahedral symmetry in which each tetrahedron tends to bind with another three by means of oxygen bridges. The members of this family, generally, have a lamellar or scaly appearance, with well-defined cleavage. They are calcium, magnesium, aluminium, sodium, iron, lithium or barium silicates. They are soft minerals, with low specific gravity and the cleavage sheets can be flexible or elastic.

(2) In particular, the particles of phyllosilicate and silica added to the sealing composition perform both a lubricating action on the composition, reducing aggregation of the particles of natural latex and therefore facilitating its passage through the dispenser valve, and at the same time an adjuvant action during sealing of the puncture as they penetrate into the latex mixture during polymerisation, performing a mechanical reinforcement action.

(3) Preferably the mineral used is silica or kaolin.

(4) Advantageously, the mineral used has an average granulometric distribution in the range between 5 and 95 nm, in particular between 10 and 30 nm.

(5) According to a preferred embodiment, the synthetic latex has average granulometry in the range between 0.05 and 0.3 m and has been advantageously used for the production of a sealing composition. Said formulation is able to considerably stabilise the sealing composition thus avoiding aggregation of the particles, while maintaining an optimal sealing power characteristic of the compositions based on natural latex.

(6) It has furthermore been noted that a diameter of the particles of synthetic latex with an average granulometric distribution in the range 0.05-0.3 m is more preferable, and even more preferably a granulometric distribution of 0.1.

(7) According to a preferred embodiment of the invention the sealing composition comprises natural latex in an amount in the range between 40 and 70%, a synthetic latex in an amount in the range between 10 and 20% and ethylene glycol in an amount in the range between 20 and 50%. More preferably the composition comprises: 30-35% of natural latex; 32-37% of synthetic latex; 25-31% of propylene glycol; 0.4-0.7% of silica having a granulometric distribution in the range between 10 and 30 nm.

(8) Preferably the synthetic latex has a gelatinisation rate of at least 25% measured according to a mechanical stability test of the Mallon type based on JIS-K6387, more preferably greater than 50%, and is advantageously selected from the group consisting of styrene-butadiene and carboxylated styrene-butadiene.

(9) Furthermore the natural latex used has given excellent results when deproteinised.

(10) The sealing composition can furthermore comprise a polyurethane latex which has a further stabilising effect and is added in an amount in the range between 0.5% and 3%, preferably 1-2%.

(11) Lastly the sealing composition can also comprise additives such as an anti-oxidant agent, preferably in an amount of 0.05-3%, more preferably 0.1-1.5%, and a stabiliser agent preferably in an amount of 0.2-3, more preferably 0.5-2%.

(12) Further characteristics of the present invention will become clear from the following description of some merely illustrative and non-limiting examples.

EXAMPLES

Example 1

(13) Chemical-Physical Characterisation of a Sealing Composition Comprising Silica

(14) The composition illustrated in Table 1 was produced according to the invention.

(15) TABLE-US-00001 TABLE 1 Quantity Components Producer (g 0.5%) Natural latex THAI Latex 314 (Thailand) Stabiliser LDBS 23 20 (Cogins) Antioxidant WLL 10 (New Tiarco) Antifreeze agent Proplylene Glycol 300 (Hengyang) Synthetic latex SBR Latex 350 (Dow) Mineral SiO.sub.2 (granule 6 dimension 15-25 nm) (Henan Wangu) Total 1000

(16) The viscosity, the pH and the specific gravity (SpG) were evaluated on different batches of the composition illustrated in Table 1. The results are given in Table 2.

(17) TABLE-US-00002 TABLE 2 Physical properties Specific Viscosity gravity Batch number (Cps) pH (SpG) 1 68.7 7.43 1.0016 2 63.3 7.44 1.0075 3 62.1 7.46 1.0087

Example 2

(18) Freezing Test

(19) The freezing test was performed on the three batches of the composition illustrated in example 1 to verify maintenance of the properties of the sealing composition also at low temperatures, in particular at 40 C.

(20) 50 ml of sealing composition were placed in a glass beaker. The beaker was then placed in a refrigerator and kept at 40 C. for 8 hours.

(21) The sample of sealing composition in all three batches analysed shows no signs of freezing or crystalline formations on the surface.

Example 3

(22) Test for Evaluation of Sealing Power

(23) The sealing power of the composition was evaluated on Ford tyres (ES8S43-19L523-AA) in which a puncture was made between the grooves with a 6 mm diameter steel nail.

(24) The reduction of the tyre pressure after 30 seconds, measured to determine a linear deflation speed in kPa/min, was higher than 50 kPa.

(25) Subsequently the tyre was fitted on a shuttle bus and connected to a compressor. The sealing composition of example 1 was injected into the tyre which was then inflated to 240 kPa.

(26) The shuttle bus was driven for 10 minutes at a minimum speed of 30 km/h and maximum speed of 80 km/h, measuring the tyre pressure to evaluate the sealing power according to the pressure loss after 3 minutes, 5 minutes and 7 minutes and verifying any leaks from the puncture made.

(27) Subsequently the shuttle bus was stopped and the pressure was measured again after 1 hour and 2 hours.

(28) The results obtained are given in Table 3.

(29) As can be seen, the sealing composition proved capable of sealing the tyre not only at ambient temperature but also at 70 C. and at 40 C. even after 5 minutes. Although at low temperatures the time required to disperse the sealing composition is considerably longer, sealing nevertheless takes place within the first 5 minutes.

(30) TABLE-US-00003 TABLE 3 Pressure Injection drop of sealing after composition Tyre inflation Tyre 30 s P0 sigillante P P P P P P temperature 250 MaxP MinP final t min 3 min 5 min 7 min 1 h 2 h Batch ( C.) (kPa) t (s) (kPa) (kPa) (psi) (s) (kPa) (kPa) (kPa) (kPa) (kPa) Sealing composition kept at ambient temperature 2 16 200 38 621 138 40 (35) 448 79 4 3 4 3 Sealing composition kept at 70 C. for 2 hours 4 70 200 29 510 97 38 (35) 407 20 7 7 14 7 1 70 200 27 483 110 39 (35) 435 27 7 7 14 7 Sealing composition kept at 40 C. for 2 hours 4 40 200 790 552 110 38 (35) 809 41 3 3 10 3 1 40 200 204 552 124 38 (35) 1024 13 6 7 10 7 2 40 205 110 469 97 37 (35) 930 3 0 3 10 7

Example 4

(31) Chemical-Physical Characterisation of a Sealing Composition Comprising Kaolin

(32) The composition illustrated in Table 4 was produced according to the invention.

(33) TABLE-US-00004 TABLE 4 Quantity Components Producer (g 0.5%) Natural latex THAI Latex 318 (Thailand) Stabiliser LDBS 23 19 (Cogins) Antioxidant WLL 10 (New Tiarco) Antifreeze agent Proplylene Glycol 285 (Hengyang) Synthetic latex SBR Latex 350 (Dow) Mineral Kaolin 18 Total 1000

(34) Viscosity, pH and specific gravity (SpG) were evaluated on different batches of the composition illustrated in Table 4. The results are given in Table 5.

(35) TABLE-US-00005 TABLE 5 Physical properties Specific Viscosity gravity Batch number (Cps) pH (SpG) Batch 4 65.3 7.20 1.0024 Batch 5 67.8 7.32 0.998 Batch 6 65.7 7.34 1.0032