THERMOPLASTIC POLYMERS FOAMED WITH A SEMICARBAZIDE

Abstract

A method of preparing a foamed thermoplastic polymer comprises contacting a chemical blowing agent (A) which is a semi-carbazide with a thermoplastic polymer or a precursor of a thermoplastic polymer. Blowing agent (A) is preferably p-toluenesulfonyl semi-carbazide and said polymer is preferably PVC. Formulations, including liquid formulations which include the blowing agent (A) and other ingredients, are also described.

Claims

1. A method of preparing a foamed thermoplastic polymer, the method comprising contacting a chemical blowing agent (A) which is a semi-carbazide with a thermoplastic polymer or a precursor of a thermoplastic polymer.

2. (canceled)

3. (canceled)

4. A method according to claim 1, wherein said blowing agent (A) is of formula ##STR00003## wherein R.sup.1 represents a sulphonyl group containing moiety and R.sup.1 represents a moiety ##STR00004## wherein the * represents the bond of moiety II by which R.sup.1 is bonded to the nitrogen atom of the semi-carbazide of Formula I; and R.sup.2 includes an optionally-substituted phenyl moiety, wherein said phenyl moiety is substituted by one or more alkyl moieties.

5. (canceled)

6. A method according to claim 1, wherein said blowing agent (A) is p-toluenesulfonyl semi-carbazide.

7. A method according to claim 4, wherein the method comprises contacting the chemical blowing agent (A) with said thermoplastic polymer during melt processing of the polymer and a liquid formulation comprising chemical blowing agent (A) is introduced directly into an extruder, wherein said liquid formulation is comprised of 20 to 30 wt % carrier, 8 to 25 wt % toluenesulfonyl semi-carbazide and 25 to 65 wt % bicarbonate, and wherein said thermoplastic polymer is melt-processed at a temperature of at least 170° C. and at a temperature not exceeding 250° C.

8. A method according to claim 7, wherein said thermoplastic polymer comprises PVC.

9. A method according to claim 8, wherein a stabiliser formulation is included with said thermoplastic polymer which comprises PVC for stabilising the PVC against degradation; wherein, said stabiliser formulation comprises a barium or calcium compound in combination with a zinc compound.

10. (canceled)

11. (canceled)

12. A method according to claim 4, wherein at least 0.05 parts by weight (pbw) of said chemical blowing agent (A) is contacted with 100 pbw of said thermoplastic polymer in the method and less than 0.4 pbw of said chemical blowing agent (A) is contacted with 100 pbw of said thermoplastic polymer in the method, wherein the sum of the pbw of calcium and zinc compounds which are associated with 100 pbw of said thermoplastic polymer in the method is at least 0.01 pbw and wherein at least 0.2 pbw of bicarbonate is contacted with 100 pbw of said thermoplastic polymer in the method.

13. (canceled)

14. (canceled)

15. A method according to claim 4, wherein the sum of the pbw of exothermic chemical blowing agents contacted with 100 pbw of said thermoplastic polymer in the method is at least 0.08 pbw and is less than 1.0 pbw; and wherein 0 pbw of azodicarbonamide is contacted with said thermoplastic polymer in the method.

16. (canceled)

17. (canceled)

18. A formulation for foaming a thermoplastic polymer, said formulation comprising: a carrier; and a chemical blowing agent (A) which is a semi-carbazide, wherein said chemical blowing agent (A) may have any feature of said chemical blowing agent (A) described in claim 1.

19. A formulation according to claim 18, wherein said formulation is a liquid formulation which includes a liquid carrier which is an organic liquid which has a boiling point of greater than 150° C. and wherein said carrier is selected from oils, esters and fatty acids; wherein, in said formulation, the ratio of the parts by weight (pbw) of carrier divided by the pbw of said blowing agent (A) is in the range 0.5 to 5; wherein said formulation includes at least 5 wt % of said chemical blowing agent (A) and less than 25 wt % of chemical blowing agent (A).

20. (canceled)

21. (canceled)

22. (canceled)

23. A formulation according to claim 18, wherein said formulation includes one or a plurality of endothermic chemical blowing agents which include a bicarbonate wherein the ratio of the sum of the wt % of exothermic blowing agent(s) divided by the sum of the wt % of endothermic blowing agent(s) in said formation is in the range 0.1 to 1; and the sum of the amounts of solid materials dispersed in the formulation is in the range of 50 to 85 wt %.

24. (canceled)

25. A formulation according to claim 23, wherein said formulation includes at least 15 wt % carrier; less than 40 wt % carrier; at least 12 wt %, of exothermic blowing agents and 30 wt % or less of exothermic blowing agents; and a chemical blowing agent (B) which is an exothermic chemical blowing agent, which is a hydrazide.

26. A formulation according to claim 18, wherein said formulation includes 0 wt % of azodicarbonamide (AZDC), and wherein said blowing agent (A) is p-toluenesulfonyl semi-carbazide.

27. A formulation according to claim 18, wherein said formulation is a liquid formulation which includes: 15 to 40 wt % carrier; 30 to 70 wt % of a bicarbonate; 5 to 25 wt %, of chemical blowing agent (A).

28. A formulation according to claim 18, wherein said formulation is a liquid formulation which includes: 20 to 30 wt % of carrier; 8 to 25 wt % of toluenesulfonyl semi-carbazide; a bicarbonate, wherein the total amount of bicarbonate in the formulation is in the range 25 to 65 wt %.

29. A formulation according to claim 28, wherein said formulation is a liquid formulation which includes 1 to 10 wt % of zinc oxide.

30. A foamed product comprising: (i) a thermoplastic polymer which is PVC; and (ii) a thiosulfinate. wherein said foamed products includes at least 100 ppm of thiosulfinate and 1000 ppm or less of thiosulfinate.

31. (canceled)

32. A formulation according to claim 29, wherein said liquid formulation includes 2 to 10 wt % of oxybissulphonyl hydrazide.

33. A formulation according to claim 19, wherein said formulation includes: 20 to 30 wt % of carrier; 8 to 25 wt % of toluenesulfonyl semi-carbazide; a bicarbonate, wherein the total amount of bicarbonate in the formulation is in the range 25 to 55 wt %, wherein said formulation includes 1 to 10 wt % of zinc oxide.

34. A formulation according to claim 28, wherein said formulation is a liquid formulation which includes 0.5 to 3 wt % of calcium oxide and 1 to 10 wt % of zinc oxide, wherein said liquid formulation includes 2 to 10 wt % of oxybissulphonyl hydrazide.

Description

EXAMPLE 1—GENERAL METHOD FOR PREPARATION OF LIQUID FORMULATIONS

[0081] Liquid formulations were prepared in a plastic container by initially mixing the ingredients by hand under ambient conditions, to incorporate the solid materials into liquid carrier. Subsequent mixing was continued using a Hamilton Beach high speed laboratory mixer until a stable homogenous dispersion had been prepared.

EXAMPLE 2 AND COMPARATIVE EXAMPLE 1—LIQUID FORMULATIONS TESTED

[0082] The general procedure described in Example 1 was used to prepare liquid formulations from the ingredients referred to in Table 1. Note that the formulation of Comparative Example C1 is the same as a currently commercially available formulation.

TABLE-US-00001 TABLE 1 Comparative Example 2 Example C1 (amount wt %) (amount wt %) Liquid carrier 24.1 24.1 Dispersant 4.25 4.25 Sodium bicarbonate 53 53 Calcium oxide 0.9 0.9 Zinc oxide 2.4 2.4 OBSH (4,4′oxybis 2.6 2.6 (benzenesulfonylhydrazide) TSSC (p-toluenesulfonylsemicarbazide) 12 0 AZDC 0 12 Fumed silica (thickener) 0.75 0.75

Testing of Materials

Test 1—Assessment of PVC Degradation Times

[0083] The liquid formulations of Example 2 and Comparative Example C1 were tested in association with PVC to assess the effect on the speed of degradation of the PVC.

[0084] In the test, 65 g of a dry blend of a PVC, stabilised by a proprietary calcium-zinc stabiliser package, was weighed into a container. 1 wt % of a liquid formulation to be assessed was added to the container and mixed manually, using a spatula, with the PVC. The mixture was then added into a Haake torque rheometer and tested at a speed of 50 rpm, over the temperature range 160-190° C. The torque curve was observed over time after the first gelation peak. In general terms, the torque increases over time due to thermal degradation. Decomposition time was determined as the time when the torque after gelation reaches a value which is 10% greater than the torque minimum.

EXAMPLE 3—TESTING OF FORMULATIONS

[0085] The formulations of Example 2 and Comparative Example C1 were added to PVC as described in Test 1 and tested as described. In addition virgin PVC (in the absence of any additive) (referred to as “Comparative Example C2”) was tested in the same way. PVC degradation times are reported in Table 2.

TABLE-US-00002 TABLE 2 Example No. PVC degradation time(s) Using Example 2 formulation 2830 Using Comparative Example C1 formulation 2457 Comparative Example C2 (virgin PVC) 2550

[0086] It should be noted from Table 2 that, by using the Example 2 formulation, the PVC takes longer to degrade (compared to Comparative Examples C1 and C2), suggesting the use of the formulation of Example 2 in foaming will result in foamed parts which have a fine cell structure and a clean white appearance. In particular, foams produced using the Example 2 formulation may be advantageous compared to foams produced using the Example C1 formulation which differs from the Example 2 formulation only in that the Example 2 formulation includes TSSC whereas the Example C1 formulation includes AZDC. Thus, use of TSSC in liquid formulations as described leads to production of improved foams.

EXAMPLE 4—PREPARATION OF FOAMS

[0087] Samples for foaming were prepared by weighing out 250 g of a dry blend of a PVC, stabilised by a proprietary calcium-zinc stabilizer package and adding 1 wt % of selected liquid formulations. The ingredients were mixed using a Waring High Speed Lab Blender for 1 minute at low speed, followed by 1 minute at high speed.

[0088] An extruder with a temperature profile as follows was started: Zone 1—170° C., Zone 2—175° C., Zone 3—180° C., Die 180° C., The RPM was increased to a set-point of 17.5 rpm. Selected mixtures including the liquid formulations as described were added to the extruder and after 3-4 minutes samples were cut and collected at the exit of the die and cooled between two metal plates.

EXAMPLE 5—TESTING OF FOAMS

[0089] Foams produced as described in Example 4 were tested as follows:

[0090] Density—cut sections were measured for density using a Alfa Mirage Densimeter.

[0091] Colour—measured using Minolta 3600d spectrophotometer, with virgin PVC resin as reference, Colour difference is quoted as ΔE.

[0092] Results are reported in Table 3.

TABLE-US-00003 TABLE 3 Example No. of formulation used in ΔE* compared to foaming Density g/cm.sup.3 Colour Virgin PVC 2 0.5404 White 1.64 C1 0.5074 Light Yellow 9.73 Virgin PVC 1.38 White —

[0093] The results in Table 3 illustrate that use of the liquid formulation of Example 2, leads to similar density reduction in the foams produced as for the existing commercially-available formulation of Example C1. However, advantageously, use of the liquid formulation of Example 2 leads to a whiter foam product which is generally white like virgin PVC and has a ΔE* which differs far less from Virgin PVC compared to the ΔE* difference when the Example C1 formulation is used to foam the PVC.

EXAMPLE 6—COMPARISON OF OTHER FORMULATIONS

[0094] The general procedure of Example 1 was used to prepare liquid formulations from the ingredients in Table 4.

TABLE-US-00004 TABLE 4 Example 7 Comparative Formulation Example C3 (amount wt %) (amount wt %) Liquid carrier 25 25 Dispersant 4 5 Sodium 35 37.5 bicarbonate Calcium oxide 1 1 Zinc oxide 2.4 OBSH (4,4′oxybis 7.8 4 (benzenesulfonylhydrazide) TSSC (P-toluenesulfonylsemicarbazide) 10 AZDC 13.8 26.5 Fumed silica (thickener) 1 1

[0095] The formulations were assessed in the torque rheometer as described in Test 1. In this regard, 1 wt % of a liquid formulation to be assessed was added to 65 g of a dry blend of PVC, stabilised by a proprietary calcium-zinc stabiliser package. The tests were conducted at 190° C., a speed of 30 rpm and a time of 6 minutes. The resulting polymer melt was removed from the mixer, pressed between two metal plates and allowed to cool in a Carver cold press.

[0096] The colours of the resulting press-outs made using the Example 7 and Comparative Example C3 formulations were assessed as was the colour of the dry blend of calcium-zinc stabilised PVC. Results are provided in Table 5.

TABLE-US-00005 TABLE 5 Test Material L*(D65) a*(D65) b*(D65) Dryblend Of calcium-zinc stabilized 81.25 2.64 18.04 PVC Foam produced using Example 7 79.47 2.13 15.41 formulation Foam produced using Example C3 74.5 3.01 17.55 formulation

[0097] It is clear from Table 5 that use of the Example 7 formulation leads to an improvement in colour compared to the Example C3 formulation which includes a higher level of AZDC.

[0098] Other liquid formulations for use in foaming PVC are detailed in Table 6.

TABLE-US-00006 TABLE 6 Amounts in formulation (wt %) Example Example Example Example Example 8 Example 9 10 11 12 13 Liquid Carrier 25 24 24 24 24 24 Dispersant 4 4 4 4 4 4 Sodium Bicarbonate 35 32 32 32 32 32 Calcium Oxide 0.9 0.9 0.9 0.9 0.9 0.9 Zinc oxide 8.9 8.9 8.9 8.9 8.9 8.9 OBSH 6.8 6.8 6.8 6.8 6.8 6.8 TSSC 18.4 18.4 18.4 18.4 18.4 18.4 Fumed Silica 1 — — — — — Talc (Magnesium — 5 — — — — Silicate) Filler (calcium — — 5 — — — carbonate) Acrylic process aid — — — 5 — — Stearic acid — — — — 5 — Decanoic acid — — — — — 5

[0099] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.