FOAMED COMPOSITION

Abstract

The invention relates to a foamed composition comprising a thermoplastic copolyester elastomer in an amount of between 70 to 99 wt % and a plasticizer in an amount of between 1 to 30 wt % based on the total amount of the composition and articles comprising the foamed composition, as well as a process for preparing such foamed composition.

Claims

1. Foamed composition comprising a thermoplastic copolyester elastomer in an amount of between 70 to 99 wt %, and a plasticizer in an amount of between 1 to 30 wt % based on the total amount of the composition.

2. Foamed composition according to claim 1, wherein the thermoplastic copolyester elastomer comprises hard segments built up from polyester repeating units derived from at least one aliphatic diol and at least one aromatic dicarboxylic acid or an ester thereof, and soft segments chosen from the group consisting of aliphatic polyether, aliphatic polyester, aliphatic polycarbonate, dimer fatty acids and dimer fatty diols and combinations thereof.

3. Foamed composition according to claim 1, wherein the hard segments are chosen from the group consisting of ethylene terephthalate (PET), propylene terephthalate (PPT), butylene terephthalate (PBT), polyethylene bibenzoate, polyethelyene naphatalate (PEN), polybutylene bibenzoate, polybutylene naphatalate, polypropylene bibenzoate and polypropylene naphatalate and combinations thereof and the soft segments are chosen from the group consisting of aliphatic polyether, aliphatic polyester, aliphatic polycarbonate, dimer fatty acids and dimer fatty diols and combinations thereof.

4. Foamed composition according to claim 2, wherein the hard segment is chosen from PBT or PET and the soft segment is chosen from the group consisting of polybutylene adipate (PBA), poly(ethylene oxide) (PEO), polypropylene oxide (PPO), polytetramethylene oxide (PTMO),), PEO-PPO-PEO and combinations thereof.

5. Foamed composition according to claim 1, wherein the amount of plasticizer is between 8 and 20 wt % with respect to the total amount of the composition.

6. Foamed composition according to claim 1, wherein the plasticizer is chosen from the group consisting of (tere)phthalates and esters thereof, dibasic acid esters, mellitates and esters thereof, cyclohexanoate esters, citrate esters, phosphate esters, modified vegetable oil esters, benzonate esters, and petroleum oils and combinations thereof.

7. Foamed composition according to claim 1, wherein the plasticizer is chosen from the group consisting of Triphenyl phosphate (TPP), tert-Butylphenyl diphenyl phosphate (Mono-t-but-TPP), di-tert-butylphenyl phenyl phosphate (bis-t-but-TPP), Tris(p-tert-butylphenyl) phosphate (tri-t-but-TPP), Resorcinol bis (Diphenyl Phosphate) (RDP), dichloropropyl phosphate, Bisphenol A bis-(Diphenyl Phosphate) (BDP), tricresyl phosphate (TCP), triethyl phosphate, tributyl phosphate (TBP), tri-2-ethylhexyl phosphate, trimethyl phosphate, epoxidized soybean oil (ESO), epoxidized palm oil (EPO), epoxidized linseed oil (ELO), argan oil and combinations thereof.

8. Foamed composition according to claim 1, wherein the density of the foamed composition is between 0.1 to 0.7 g/cm3.

9. Foamed composition according to claim 2, wherein the soft segment is chosen from the group consisting of poly(ethylene oxide) (PEO), polypropylene oxide (PPO) and polytetramethylene oxide (PTMO), PEO-PPO-PEO, and combinations thereof and the density of the foamed composition is between 0.10 and 0.30 g/cm3.

10. Article comprising the foamed composition according to claim 1.

11. Article according to claim 10, wherein the article is a inner shoe sole or a midsole.

12. Process for preparing a foamed composition according to claim 1, comprising the following steps: a. Providing a composition comprising a thermoplastic copolyester elastomer in an amount of between 70 to 99 wt %, and a plasticizer in an amount of between 1 and 30 wt % based on the total amount of the composition; b. Bringing the composition to a foaming temperature of between (Tm-100) C. and Tm, in which Tm is the melting temperature of the hard segment of the thermoplastic copolyester elastomer composition as measured according to ISO 11357-1:1997 by DSC in the second heating curve, with a heating and cooling rate of 10 C. per min, under nitrogen atmosphere; c. Providing a physical blowing agent under pressure to the composition while maintaining the pressure and allowing the physical blowing agent to substantially dissolve in the composition; d. Releasing the pressure thereby forming the foamed composition.

13. Process according to claim 12 wherein the composition comprising thermoplastic copolyester elastomer comprises hard segments chosen from PBT or PET and soft segments chosen from the group consisting of polybutylene adipate (PBA), poly(ethylene oxide) (PEO), polypropylene oxide (PPO), polytetramethylene oxide (PTMO),), PEO-PPO-PEO and combinations thereof and the plasticizer is chosen from group consisting of Triphenyl phosphate (TPP), tert-Butylphenyl diphenyl phosphate (Mono-t-but-TPP), di-tert-butylphenyl phenyl phosphate (bis-t-but-TPP), Tris(p-tert-butylphenyl) phosphate (tri-t-but-TPP), Resorcinol bis (Diphenyl Phosphate) (RDP), dichloropropyl phosphate, Bisphenol A bis-(Diphenyl Phosphate) (BDP), tricresyl phosphate (TCP), triethyl phosphate, tributyl phosphate (TBP), tri-2-ethylhexyl phosphate, trimethyl phosphate, epoxidized soybean oil (ESO), epoxidized palm oil (EPO), epoxidized linseed oil (ELO), argan oil and combinations thereof.

Description

EXAMPLES

Materials Used

[0054] Elastomer A: A copolyether-ester elastomer comprising 55 wt % polytetramethylene oxide soft segment and poly butylene terephthalate (PBT) hard segment, having a shore D hardness of 33 (ISO 868) and MFI of 33 cm.sup.3/10 min at 2.16 kg load at 230 C. (ISO 1133) and a melting temperature of the hard segment in the thermoplastic copolyester elastomer being 161.5 C. as measured with DSC according to ISO 11357-1:1997 in the second heating curve, with a heating and cooling rate of 10 C. per min, under nitrogen atmosphere.

[0055] ESO: epoxidized soybean oil

[0056] Phosflex: Phosflex 71B HP, which is a blend of TPP, mono-t-But-TPP, Bis-t-But-TPP, Tri-t-But-TPP.

[0057] BDP: Bisphenol A bis-(Diphenyl Phosphate)

Sample Preparation

[0058] The compositions for foaming were prepared by compounding Elastomer A with varying plasticizer types and amounts as listed in Table 1. The melting temperature listed in Table 1 is the peak melting temperature of the hard segment in the thermoplastic copolyester elastomer composition during second heating cycle in a DSC at heating and cooling rates of 10 C./min under nitrogen atmosphere. Subsequently, plates were injection molded with lateral dimensions of 80*80 mm and different thicknesses as listed in Table 1. Samples with lateral dimensions of 15*15 mm were cut out of these plates for foaming tests.

Foaming

[0059] The sample with lateral dimensions of 15*15 mm and thickness as listed in Table 1 was placed in a pressure vessel that was electrically heated to the foaming temperature listed in Table 1. In Example 13, granules (also referred to as beads) of the specified composition with dimensions ranging between 3 and 5 mm were placed in a pressurized vessel that was electrically heated to the foaming temperature listed in Table 1. [0060] Subsequently, cavity was filled with CO.sub.2 at the pressure listed in Table 1 by a CO.sub.2 canister connected to the pressure vessel via a booster pump [0061] The composition was allowed to absorb CO.sub.2 for the soaking time listed in Table 1 [0062] The pressure vessel was opened, thus achieving a fast pressure drop resulting in the foamed composition. [0063] Samples were visually inspected within one minute after opening the pressure vessel for bubbles on the surface, indicating the presence of cracks in the interior of the sample. Examples of samples showing indications of cracks are depicted in FIG. 1 right column. The left column of FIG. 1 shows a sample containing no cracks. [0064] Volume of the sample was determined by measuring length, width, and thickness using a vernier gauge after 24 hours after foaming to allow the CO.sub.2 still present in the sample to diffuse out. Mass of the sample was determined by weighing and density of the sample was determined by dividing mass by volume.

TABLE-US-00001 TABLE 1 T.sub.m of CO.sub.2 Foaming Sample Soaking composition Pressure Temperature Density Thickness time Material Plasticizer ( C.) (bar) ( C.) (g/cm.sup.3) (mm) (min) Cracks Comp Ex A Elastomer A 161.5 200 115 0.34 2 15 no Comp Ex B Elastomer A 161.5 200 120 0.32 2 15 no Comp Ex C Elastomer A 161.5 200 125 0.28 2 15 no Comp Ex D Elastomer A 161.5 200 130 0.22 2 15 yes Ex1 Elastomer A 5% ESO 160.5 200 115 0.23 4 25 no Ex2 Elastomer A 10% ESO 160.1 200 120 0.24 3.4 15 no Ex3 Elastomer A 10% ESO 160.1 200 125 0.22 3.4 15 no Ex4 Elastomer A 15% ESO 160.0 200 110 0.24 4 25 no Ex5 Elastomer A 20% ESO 159.7 200 100 0.26 4 25 no Ex6 Elastomer A 10% Phosflex 158.4 200 110 0.22 4 25 no Ex7 Elastomer A 10% Phosflex 158.4 140 110 0.23 4 25 no Ex8 Elastomer A 10% Phosflex 158.4 140 110 0.26 2 15 no Ex9 Elastomer A 10% Phosflex 158.4 140 115 0.23 2 15 no Ex10 Elastomer A 10% BDP 159.9 200 115 0.24 4 25 no Ex11 Elastomer A 20% BDP 157.5 200 115 0.22 4 25 no Ex12 Elastomer A 20% BDP 157.5 200 120 0.19 4 25 no Ex13 Elastomer A 10% ESO 160.5 200 140 0.12 Beads: 3-5 mm 5 no FIG. 2 provides a graph in which the resultant foam density in (g/cm.sup.3) (y-axis) is shown against the foaming temperature in C. (x-axis). Comparative experiments A-D are shown as .square-solid. filled square. The figure shows that either only high densities without cracks
(Comp Ex A-C), or low densities with cracks could be obtained (Comparative experiment D). For the examples comprising a plasticizer, much lower densities could be obtained, without crack formation (see examples 1 to 13 in FIG. 2). The described examples show that without the addition of plasticizer it is not possible to produce crack-free foams with density lower than 0.28 g/cm.sup.3 (see Comparative experiments A to D), whereas the addition of plasticizer to the composition enabled the production of crack-free foams with densities as low as 0.19 g/cm.sup.3 (see Examples 1 to 12). For granules, crack-free foams with densities as low as 0.12 g/cm.sup.3 were reached (see Example 13).