Method for treating polyvinyl butyral (PVB)

Abstract

The present invention relates to a method for treating fragments of polyvinyl butyral (PVB) in which glass shards are encrusted in or on the surface of the PVB. The method involves placing PVB fragments in contact with an aqueous solution comprising a cationic surfactant and a weak base, to obtain a mixture. This mixture, subjected to ultrasound within a defined temperature range, leads to separation of the glass shards and the PVB. In particular, the inventors have discovered that the combined, simultaneous, and complementary action of a weak base, a cationic surfactant, and ultrasound, at an appropriate temperature, made it possible to detach and/or unembed the glass shards fixed to the collected PVB without degrading the polymer matrix.

Claims

1. Method for treating fragments of polyvinyl butyral (PVB) having glass shards in or on the surface of the PVB, the method comprising the following steps: bringing the PVB fragments into contact with an aqueous solution comprising a cationic surfactant and a weak base, to obtain a mixture, subjecting said mixture to ultrasound, and separating the glass shards and the PVB, the temperature of the mixture subjected to ultrasound being between 40 and 70° C.

2. Method according to claim 1, further comprising a step of separating: a) said aqueous solution comprising a cationic surfactant and a weak base, b) the glass shards, and c) the PVB.

3. Method according to claim 2, wherein the separation step is carried out by filtration, sedimentation, decantation, or centrifugation.

4. Method according to claim 1, further comprising, after the step of subjecting the mixture to ultrasound, a step of rinsing the PVB with water and air drying the PVB.

5. Method according to claim 1, wherein the weak base has the following general formula:
M.sub.2CO.sub.3,  Formula (I): where M represents an alkali metal.

6. Method according to claim 5, wherein the weak base is potassium carbonate or sodium carbonate.

7. Method according to claim 1, wherein said aqueous solution comprising a cationic surfactant and a weak base has a basic pH of between 8 and 14.

8. Method according to claim 1, wherein the temperature of the mixture subjected to ultrasound is between 45 and 65° C.

9. Method according to claim 1, wherein the cationic surfactant is a quaternary ammonium halide salt.

10. Method according to claim 9, wherein the cationic surfactant is a quaternary ammonium salt corresponding to the following general formula (II): ##STR00002## where R.sub.1 to R.sub.3 each represent a methyl group, R.sub.4 represents a linear or branched alkyl chain, and where X represents a halide.

11. Method according to claim 1, wherein the cationic surfactant has an HLB between 20 and 25.

12. Method according to claim 1, wherein the cationic surfactant is a cetyltrimethylammonium halide salt.

13. Method according to claim 7, wherein the basic pH is between 11 and 13.

14. Method according to claim 8 wherein the temperature is between 50 and 60° C.

15. Method according to claim 8 wherein the temperature is between 55 and 58° C.

16. Method according to claim 10 wherein R.sub.4 represents a linear alkyl chain.

17. Method according to claim 16 wherein the linear alkyl chain comprises from 8 and 30 carbon atoms.

18. Method according to claim 16 wherein the linear alkyl chain comprises, from 10 and 24 carbon atoms.

19. Method according to claim 16 wherein the linear alkyl chain comprises from 10 and 18 carbon atoms.

20. Method according to claim 1 wherein the matrix of the PVB or the mechanical properties of the PVB are not degraded by the method.

Description

DESCRIPTION OF FIGURES

(1) FIG. 1 is a SEM image (magnification ×621) of a PVB sample before treatment.

(2) FIG. 2 is a SEM image (magnification ×73) of a PVB sample before (left) and after treatment (right) deposited on the same stub (covered with carbon adhesive, in the center)

(3) FIG. 3 is a SEM image (magnification ×621) of a PVB sample after treatment.

EXAMPLE 1

(4) One hundred grams of pieces of PVB sheets obtained from crushing laminated glass (PVB fragments) are immersed in an aqueous solution 1 liter in volume comprising 53 grams sodium carbonate (0.5 mol) and 0.655 g cationic surfactant (0.0018 mol cetrimonium bromide close to its critical micelle concentration at the treatment temperature). The mixture is subjected to ultrasound produced by an Elmasonic P30H tank with an ultrasonic power of 100 Watts delivered at a frequency of 80 kHz, for 1.5 hours. The temperature of the reaction medium stabilizes between 55 and 58° C. A conventional mechanical stirring device ensures dispersion of the PVB fragments in the medium.

(5) When stopped, the pieces of treated plastic (PVB) settle and are collected, then are rinsed with water and air dried.

(6) Measurement of the Residual Glass Content:

(7) Estimation by counting glass shards under an optical microscope and analysis of the silicon content by EDX probe reveal a residual glass content of less than 30 milligrams per square meter of PVB.

EXAMPLE 2

(8) One hundred grams of pieces of PVB sheets obtained from crushing laminated glass (PVB fragments) are immersed in an aqueous solution 1 liter in volume comprising 69 grams potassium carbonate (0.5 mol) and 2 g cationic surfactant (0.0063 mol cetrimonium chloride close to its critical micelle concentration at the treatment temperature). The mixture is subjected to ultrasound produced by an Elmasonic P30H tank with an ultrasonic power of 120 Watts delivered at a frequency of 37 kHz, for 1.5 hours. The temperature of the reaction medium stabilizes between 55 and 58° C. A conventional mechanical stirring device ensures dispersion of the PVB fragments in the bath.

(9) When stopped, the pieces of treated plastic (PVB) settle and are collected, then are rinsed with water and air dried.

(10) Measurement of the Residual Glass Content:

(11) Estimation by counting glass shards under an optical microscope and analysis of the silicon content by EDX probe reveal a residual glass content of around 50 milligrams per square meter of PVB.

EXAMPLE 3

(12) One hundred grams of pieces of PVB sheets obtained from crushing laminated glass (PVB fragments) are immersed in an aqueous solution 1 liter in volume comprising 53 grams sodium carbonate (0.5 mol) and 0.655 g cationic surfactant (0.0018 mol cetrimonium bromide close to its critical micelle concentration at the treatment temperature). The mixture is subjected to ultrasound produced by an Elmasonic P30H tank with an ultrasonic power of 120 Watts delivered at a frequency of 37 kHz, for 0.5 hours in the water-filled tank. The ultrasound frequency is then changed to the value of 80 kHz for 0.5 hour at the ultrasonic power of 100 Watts. The temperature of the reaction medium stabilizes between 55 and 58° C. A conventional mechanical stirring device ensures dispersion of the PVB fragments in the bath throughout the operation.

(13) When stopped, the pieces of treated plastic (PVB) settle and are collected, then are rinsed with water and air dried.

(14) Measurement of the Residual Glass Content:

(15) Estimation by counting glass shards under an optical microscope and analysis of the silicon content by EDX probe reveal a residual glass content of less than 30 milligrams per square meter of PVB.

COMPARATIVE EXAMPLES

(16) For comparative purposes, various tests were carried out according to the protocol of Examples 1 or 2 or 3 while varying the nature of the surfactant and of the base, their presence or absence, the frequency of the ultrasound, and the temperature of the reaction medium.

(17) The results are presented in Table 1.

(18) Results:

(19) TABLE-US-00001 TABLE 1 Surfactant Base Ultrasound Conditions Analysis Example 1 Cetrimonium Na.sub.2CO.sub.3 100 Watts <30 mg bromide at 80 kHz glass/m.sup.2 PVB Example 2 Cetrimonium K.sub.2CO.sub.3 120 Watts about 50 mg chloride at 37 kHz glass/m.sup.2 PVB Example 3 Cetrimonium Na.sub.2CO.sub.3 120 Watts <30 mg bromide at 37 kHz glass/m.sup.2 PVB then at 80 kHz Comparative None Na.sub.2CO.sub.3 100 Watts According to protocol 0.8 to 1.6 g example 1 at 80 kHz of Example 1 without glass/m.sup.2 PVB addition of surfactant Comparative Cetrimonium K.sub.2CO.sub.3 No According to protocol 1 to 2 g example 2 chloride ultrasound of Example 2 without glass/m.sup.2 PVB ultrasound Comparative Cetrimonium None 100 Watts According to protocol 0.8 to 1.6 g example 3 bromide at 80 kHz of Example 1 without glass/m.sup.2 PVB addition of base Comparative Non-ionic K.sub.2CO.sub.3 120 Watts According to protocol 2 g example 4 surfactant at 37 kHz of Example 2 glass/m.sup.2 PVB Triton TX100 Comparative Anionic K.sub.2CO.sub.3 120 Watts According to protocol 0.3 to 0.8 g example 5 surfactant at 37 kHz of Example 3 glass/m.sup.2 PVB SDS then at 80 kHz Comparative Cetrimonium Na.sub.2CO.sub.3 120 Watts According to protocol 3 to 5 g example 6 bromide at 37 kHz of Example 3 but with glass/m.sup.2 PVB then at 80 kHz the temp of the reaction medium stabilized between 35 and 38° C.

CONCLUSION

(20) The detachment of glass shards carried out in the absence of one of the four factors (base, cationic surfactant, ultrasound, and temperature) led to unsatisfactory results.

(21) In particular, outside the claimed temperature ranges, the separation of glass shards and PVB is not satisfactory. Similarly, the use of an anionic or non-ionic surfactant does not allow satisfactory results to be obtained.

(22) It is undoubtedly the combination of the four factors acting together that produces a significant effect in terms of extraction/detachment of glass shards from the surface of the PVB.