PROCESS FOR PREPARING THERMOPLASTIC RESIN

Abstract

The invention relates to a process for preparing a thermoplastic resin comprising the following steps: a) mixing: a thermoplastic copolyester (A) having a shore A hardness of less than 95; and a silicone elastomer (B) comprising a polydiorganosiloxane gum having a plasticity of at least 30 and having on average at least 2 alkenyl groups per polymeric chain and optionally a reinforcing agent in the range of 0 to 50 wt % based on the weight of the polydiorganosiloxane gum; and a radical initiator (C) in an amount of 0.01 to 5 wt % based on the weight of the silicone elastomer; and optionally an adhesion additive (D); wherein the weight ratio of the silicone elastomer to the thermoplastic copolyester (B:A) is from 15:85 to 99.5:0.5; b) dynamically vulcanizing the silicone elastomer in the thermoplastic copolyester at an elevated temperature. The invention also relates to a thermoplastic resin itself.

Claims

1. Process for preparing a thermoplastic resin comprising the following steps: a) mixing: a thermoplastic copolyester (A) having a shore A hardness of less than 95; and a silicone elastomer (B) comprising a polydiorganosiloxane gum having a plasticity of at least 30 and having on average at least 2 alkenyl groups per polymeric chain and optionally a reinforcing agent in the range of 0 to 50 wt % based on the weight of the polydiorganosiloxane gum; and a radical initiator (C) in an amount of 0.01 to 5 wt % based on the weight of the silicone elastomer; and optionally an adhesion additive (D); wherein the weight ratio of the silicone elastomer to the thermoplastic copolyester (B:A) is from 15:85 to 99.5:0.5; b) dynamically vulcanizing the silicone elastomer in the thermoplastic copolyester at an elevated temperature.

2. Process according to claim 1, wherein the silicone elastomer (B) comprises a reinforcing agent being a silica filler.

3. Process according to claim 1, wherein the thermoplastic copolyester comprises hard segments of polyethylene terephthalate (PET) and/or polybutylene terephthalate (PBT).

4. Process according to claim 1, wherein the thermoplastic copolyester comprises soft segments chosen from polytetramethylene oxide (PTMO), polyethylene oxide (PEO), polypropylene oxide (PPO), block copolymers of polyethylene oxide) and polypropylene oxide), linear aliphatic polycarbonates, polybutylene adipate (PBA) and derivates of dimer fatty acids or dimer fatty acid diols, polyolefins, linear aliphatic polyesters and combinations thereof.

5. Process according to claim 1, wherein the content of silicone elastomer in the thermoplastic resin is between 5 and 30 wt %, with wt % being with respect to the total weight of the thermoplastic resin.

6. Process according to claim 1, wherein the adhesion additive (D) comprises a polyolefin comprising an acrylate, maleic anhydride, and/or acid functionality.

7. Process according to claim 1, wherein the polydiorganosiloxane gum has a molecular weight (Mn) of at least 10,000 g/mol and not more than 1,000,000 g/mol.

8. Process according to claim 1, wherein the polydiorganosiloxane gum comprises organic groups being alkyl and substituted alkyl radicals, alkenyl radicals, cycloalkyl radicals, aromatic hydrocarbon radicals and combinations thereof.

9. Process according to claim 1, wherein the polydiorganosiloxane gum is terminated with a vinyl group and/or contains at least one vinyl group as a pendant group

10. Thermoplastic resin prepared by the process according to claim 1.

11. Thermoplastic resin comprising as dispersed phase a silicone elastomer compound comprising a radically cross-linked polydiorganosiloxane and as continuous phase a copolyester compound comprising a thermoplastic copolyester wherein the weight ratio of the continuous phase to the dispersed phase is from 99.5:0.5 to 15:85, wherein the dispersed phase may comprise up to 50% by weight of a reinforcing filler.

12. Thermoplastic resin according to claim 10, wherein the thermoplastic resin has a shore A hardness of less than 80.

13. Thermoplastic resin according to claim 11, wherein the thermoplastic copolyester comprises hard segments of PBT and/or PET and soft segments chosen from polytetramethylene oxide (PTMO), polyethylene oxide (PEO), polypropylene oxide (PPO), block copolymers of poly(ethylene oxide) and poly(propylene oxide), linear aliphatic polycarbonates, polybutylene adipate (PBA) and derivates of dimer fatty acids or dimer fatty acid diols, polyolefins, linear aliphatic polyesters and combinations thereof.

14. Soft goods comprising the thermoplastic resin of claim 10.

Description

EXAMPLES

Materials

[0051] (A) thermoplastic copolyester: thermoplastic copolyester containing 75 wt % of soft segment being PTHF with Mw 3000 g/mol and 25 wt % of hard segment being PBT, wherein wt % is with respect to the total weight of thermoplastic copolyester.

[0052] (A1) thermoplastic copolyester: thermoplastic copolyester containing 40 wt % of soft segment being dimerised fatty acid and 60 wt % of hard segment being PBT, wherein wt % is with respect to the total weight of thermoplastic copolyester.

[0053] The silicone elastomer (B) was a polydiorganosiloxane gum having an Mn of 60,000 and having 300 ppm of a vinyl functionality with 5 wt % of a precipitated silica having a surface area of 250 m.sup.2/g as reinforcing agent and the radical initiator (C) was 0.1 wt % of a dicumyl peroxide, based on the weight of the silicone elastomer.

[0054] The adhesion additive (D) was a polyethylene based tertpolymer having functionality of methyl acrylate and glycidyl methacrylate.

[0055] Thermoplastic resin with 10 wt % and 20 wt % of silicone elastomer, wherein wt % is with respect to the thermoplastic resin were prepared as follows: 89 wt % of thermoplastic copolyester (A), 1 wt % adhesion additive (D), 9.9 wt % silicone elastomer (B) and 0.1 wt % of a radical initiator (C), in which wt % is with respect to the total weight of thermoplastic resin, were mixed and dynamically vulcanized using an extruder at a temperature of about 200 C.

78 wt % thermoplastic copolyester (A), 2 wt % adhesion additive (D), 19.8 wt % silicone elastomer (B), and 0.2 wt % of a radical initiator (C), in which wt % is with respect to the total weight of thermoplastic resin, were mixed and dynamically vulcanized using an extruder at a temperature of about 200 C.

[0056] Thermoplastic resin with thermoplastic copolyester (A1) and 9.9 wt % and 14.85 wt % of silicone elastomer, wherein wt % is with respect to the thermoplastic resin were prepared as follows:

89.5 wt % of thermoplastic copolyester (A1), 0.5 wt % adhesion additive (D), 9.9 wt % silicone elastomer (B) and 0.1 wt % of a radical initiator (C), in which wt % is with respect to the total weight of thermoplastic resin, were mixed and dynamically vulcanized using an extruder at a temperature of about 200 C.
83 wt % thermoplastic copolyester (A1), 2 wt % adhesion additive (D), 14.85 wt % silicone elastomer (B), and 0.15 wt % of a radical initiator (C), in which wt % is with respect to the total weight of thermoplastic resin, were mixed and dynamically vulcanized using an extruder at a temperature of about 200 C.

[0057] A blend of thermoplastic copolyester (A) and 17 wt % of epoxidized soybean oil (ESO), wt % with respect to the total weight of the blend, was prepared by mixing the thermoplastic copolyester and the plasticizer using an extruder at a temperature of about 195 C.

[0058] TPSiV 4000-70A thermoplastic elastomer: Commercially available, TPU-based material.

Measured Properties

Shore a Hardness:

[0059] Hardness has been measured on a Shore A scale according to the norm ISO 868. Prior to the measurement samples were conditioned for 24 hrs at 23 C. and 50% rel. humidity. Measuring time was 3 sec.

Tensile Properties:

[0060] Tensile properties were measured according to the norm ISO527/1BA. Test temperature was 23 C. Prior to test tensile bars were conditioned for 24 hrs at ambient conditions (23 C. and 50% rel. humidity). Test speed was 500 mm/min for tensile stress and strain.

Scratch Resistance Test:

[0061] An inhouse scratch performance evaluation was performed using a Falex scratch tester with a spherical ruby ball indenter. A fixed normal load was applied and then a 20 mm long scratch was made at 10 mm/sec. The applied loads were varied between (1, 2.5, 5, 10 N) with indenters of diameter 2 or 5 mm. Samples were injection molded plates (120 mm120 mm2 mm) with smooth surface. After scratches were made for the different diameters and applied loads, they were rated by how visible the scratches were by three people. Testing was performed at ambient conditions (23 C and 50% rel. humidity). ++ denotes highest scratch resistance, thus lowest amount of scratches visible, and 0 denotes worst scratch resistance, thus high amount of scratches visible.

Tear Strength Test:

[0062] Tear strength has been measured according to the norm ISO 34/Method A. Samples were 2 mm thick. Test speed for tear strength test was 100 mm/min. Tear strength has been measured both in flow direction and transverse direction. The load at yield point was regarded as tear strength, which is not consistent with conception of method A.

Spiral Flow Measurement:

[0063] Samples were injection molded at three different pressures: 800, 1000 and 1200 bar into a predefined G-shaped mold. Melt temperature was 190 C., mold temperature 40 C. and injection speed 30 mm/s. Spiral flow length was determined and results are given in Table 1.

[0064] Stain resistance test discoloration ASTM E308/F2:

[0065] Color ((L, a and b according to ASTM E308/F2) of material was measured prior to and after staining. Color change, delta E, was then calculated using following formula:

E*=[(L).sup.2+(a).sup.2+(b).sup.2].sup.1/2.

[0066] Dye was poured into cup and samples were submerged into dye for 5 min and 30 min. After submerging, samples were wiped and dried with a dry cloth. Colors were again measured and samples were weighed. Color change (delta E) is provided in Table 1. Dye used was RIT Liquid Dye Denim Blue.

TABLE-US-00001 TABLE 1 Results Comparative A1 Example 1 Example 2 Example 3 Comparative A Thermoplastic (A) + 9.9 wt % (A) + 19.8 wt % (A1) + 9.9 wt % Thermoplastic copolyester silicone silicone silicone copolyester (A) (A1) elastomer elastomer elastomer Properties Hardness Shore A 82 78 67 Hardness Shore D 23 45 37 Modulus [MPa] 19 85 13 11 Tear strength flow 44 32 21 41 direction [N/mm] Tear strength 45 34 22 54 transverse direction [N/mm] Scratch resistance 0 Not measured ++ Stain resistance of 2.6 1.0 liquid denim blue dye 5 min; delta E Stain resistance of 3.6 2.4 liquid denim blue dye 30 min; delta E Spiral flow length at 10.6 13.2 800 bar [cm] Spiral flow length at 12.2 16.2 1000 bar [cm] Spiral flow length at 15.0 18.5 1200 bar [cm] Example 4 (A1) + 14.85 wt % Comparative B Comparative C silicone Blend of (A) TPSiV 4000- elastomer with plasticizer 70A Properties Hardness Shore A 67 68 Hardness Shore D 35 Modulus [MPa] 10 Tear strength flow 40 34 14 direction [N/mm] Tear strength 54 33 16 transverse direction [N/mm] Scratch resistance 0 + Stain resistance of liquid denim blue dye 5 min; delta E Stain resistance of liquid denim blue dye 30 min; delta E Spiral flow length at 12.6 7.4 800 bar [cm] Spiral flow length at 15.5 9.3 1000 bar [cm] Spiral flow length at 18.4 11.2 1200 bar [cm]

[0067] The results in Table 1 clearly show that with the method according to the present invention a thermoplastic resin may be obtained, which combines softness (lower Shore A hardness) in combination with sufficient tear strength, and scratch resistance. When compared to a blend, the scratch resistance is much better with the method according to the invention. When compared with the commercially available TPSiV solution, the tear strength was much better with the method according to the invention.