THERMOPLASTIC COMPOSITION

Abstract

This disclosure relates to a shaped article made from thermoplastic material which may be a thermoplastic elastomeric material containing a masterbatch of a stick-slip modifier having one or more thermoplastic silicone vulcanisates, an assembly comprising the article and a process for making the shaped article.

Claims

1. A shaped article of a thermoplastic material comprising a blend of (A) one or more thermoplastic organic materials, with (B) a masterbatch of a stick-slip modifier comprising (B1) one or more thermoplastic organic materials, (B2) a silicone elastomer; and/or (B3) an uncured organopolysiloxane polymer in which masterbatch (B) there is contained a total of from 20% to 60% by weight of components (B2)+(B3) based on the weight of (B1)+(B2)+(B3) and in which thermoplastic elastomer composition there is a total of from 0.2 to 25% by weight of cross-linked silicone elastomer based on the weight of (A)+(B).

2. A shaped article in accordance with claim 1 comprising component (B2) and optionally component (B3).

3. A shaped article in accordance with claim 2 wherein uncured organopolysiloxane (B3) is present in an amount of from 0.1 to 25% by weight of masterbatch (B).

4. A shaped article in accordance with claim 1 wherein Silicone elastomer (B2), when present, is prepared by dynamic vulcanisation of: diorganopolysiloxane (B2a1) having an average of at least two alkenyl groups per molecule and either (i) an organopolysiloxane having at least two Si-bonded hydrogen atoms, alternatively at least three Si-bonded hydrogen atoms per molecule (B2a2) and a hydrosilylation catalyst (B2a3) and optionally a catalyst inhibitor (B2a5); or a radical initiator (B2a4); or a silanol terminated diorganopolysiloxane (B2b1), organopolysiloxane having at least two Si-bonded hydrogen atoms, alternatively at least three Si-bonded hydrogen atoms per molecule (B2a2) and a condensation catalyst (B2b3).

5. A shaped article in accordance with claim 4 wherein diorganopolysiloxane (B2a1) or diorganopolysiloxane (B2b1) is a gum having a Williams plasticity value of at least 100mm/100 as measured by ASTM D-926-08.

6. A shaped article in accordance with claim 1 wherein the one or more thermoplastic organic materials (A) and (B1) may be the same or different and are selected from polycarbonates (PC); blends of polycarbonates with other polymers; polyamides and blends of polyamides with other polymers; polyesters; polyphenylene ether (PPE) and polyphenyleneoxide (PPO), and blends of PPE or PPO with styrenics; polyphenylene sulphide (PPS), polyether sulphone (PES), polyaramids, polyimides, phenyl-containing resins having a rigid rod structure, styrenic materials; polyacrylates, SAN; halogenated plastics exemplified by; polyketones, polymethylmethacrylate (PMMA), Polyolefins as well as , copolymers and blends of polyolefin; thermoplastic elastomers such as thermoplastic urethanes, thermoplastic polyolefinic elastomers, thermoplastic vulcanizates; styrene ethylene butylene styrene (SEBS) copolymer, natural products such as cellulosics, rayon, and polylactic acid and mixtures thereof.

7. A shaped article in accordance with claim 6 wherein the one or more thermoplastic organic materials (A) and (B1) may be selected from polyesters, polycarbonates; blends polycarbonate-acrylonitrile-butadiene-styrene (PC/ABS) blends, polycarbonate-polybutylene terephthalate (PC/PBT) blends; polycaprolactam (Nylon-6), polylauryllactam (Nylon-12), polyhexamethyleneadipamide (Nylon-6,6), polyhexamethylenedodecanamide (Nylon-6,12), poly(hexamethylene sebacamide (Nylon 6,10), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), and polyethylene naphthalate (PEN); polyphenylene ether (PPE) and polyphenyleneoxide (PPO), and blends of PPE or PPO with styrenics such as high-impact3 polystyrene (HIPS), polystyrene, acrylonitrile-butadiene-styrene-(ABS) and styrene acrylonitrile resins (SAN); polyphenylene sulphide (PPS), polyether sulphone (PES), polyaramids, polyimides, ABS (acrylonitrile-butadiene-styrene), polystyrene (PS) HIPS; polyacrylates, SAN; polyvinyl chloride, fluoroplastics, and any other halogenated plastics; polyketones, polymethylmethacrylate (PMMA), polypropylene (PP), polyethylene (PE), high density polyethylene (HDPE) and low density polyethylene (LDPE), polybutene (PB) as well as copolymers and blends of polyolefin, thermoplastic urethanes, thermoplastic polyolefinic elastomers, thermoplastic vulcanizates; and styrene ethylene butylene styrene (SEBS) copolymer.

8. A shaped article in accordance with claim 6, wherein the one or more thermoplastic organic materials (A) and (B1) may be selected from polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, ABS (acrylonitrile-butadiene-styrene), polystyrene (PS), and high-impact polystyrene (HIPS), polyacrylates, styrene-acrylonitrile resins (SAN) and any blends thereof.

9. A shaped article in accordance with claim 1 wherein the shaped article is an automobile part such as a housing, latch, window winding system, wiper part, sun roof part, lever, bush, gear, gear box part, pivot housing, bracket, zipper, switch, cam, sliding element or plate and as a part of door panel decorative trims, arm rests, central console, dashboards, glove boxes, seats and/or a combination of parts in frictional contact with the sliding member.

10. An assembly comprising: a shaped article in accordance with claims 1 in frictional contact with a sliding member, the shaped article and the sliding member being configured to remain in frictional contact and move relative to each other.

11. An assembly in accordance with claim 10 wherein the sliding member is a second shaped article in accordance with claim 1.

12. An assembly in accordance with claim 10 wherein the sliding member is a non-plastic material.

13. An assembly in accordance with claim 10 wherein the assembly is door panel decorative trims, arm rests, central console, dashboards, glove boxes, seats or a combination of parts in frictional contact including the shaped article and sliding member.

14. A method for making a shaped article in accordance with claim 1 comprising making a masterbatch of a stick-slip modifier (B) comprising (B1) one or more thermoplastic organic materials, (B2) a silicone elastomer; and/or (B3) an uncured organopolysiloxane polymer (i) by blending uncured organopolysiloxane polymer (B3) and/or the components used to produce silicone elastomer (B2) silicone composition with one or more thermoplastic organic materials (B1), (ii) when the silicone elastomer (B2) is being made, dynamically vulcanising the silicone composition to form silicone elastomer (B2), and/or (iii) when the silicone elastomer (B2) is being made, introducing (B3), during step (ii) or after step (iii); in which masterbatch (B) there is contained from a total of from 20% to 60% by weight of components (B2)+(B3) based on the weight of (B1)+(B2)+(B3) and in which thermoplastic elastomer composition there is a total of from 0.2 to 25% by weight of cross-linked silicone elastomer based on the weight of (A)+(B) and shaping the thermoplastic material to form a shaped article.

15. A method in accordance with claim 14 wherein the shaped article is shaped by extrusion, vacuum forming, injection moulding, blow moulding, 3D printing or compression moulding, to fabricate plastic parts.

16. A method of making an assembly comprising making a shaped article in accordance with claim 14 and fixing or placing said shaped article in frictional contact with a sliding member, the shaped article and the sliding member being configured to remain in frictional contact and move relative to each other.

17. Method of reducing the occurrence of stick-slip interactions of a thermoplastic material comprising combining a a thermoplastic silicone vulcanisate with a masterbatch.

18. A shaped article of a thermoplastic material in accordance with claim 1 wherein the thermoplastic material is a thermoplastic elastomeric material.

Description

EXAMPLES

[0174] The invention is illustrated by the following examples, in which parts and percentages are by weight unless otherwise stated.

[0175] Silicone rubber masterbatches were prepared using two silicone rubber bases in the amounts depicted in Table 1 below using the materials described. [0176] i) Si-rubber base 1 is an uncatalysed Silicone Rubber Base of 70 Shore A hardness (measured in accordance with ASTM D2240-03) comprising a blend of organopolysiloxane gums, and silica filler. The blend of gums is a mixture of vinyldimethyl terminated polydimethylsiloxane, vinyldimethyl terminated polydimethyl methylvinyl siloxane copolymer gum and a trimethyl terminated polydimethyl methylvinyl siloxane copolymer. The gum has a specific gravity of 1.23 and the gum blend has a Williams Plasticity number comprised between 300 and 450 mm/100, measured in accordance with ASTM D-926 - 08. [0177] ii) The silica used as reinforcing filler is a fumed (pyrogenic) silica with a particle size comprised in the range of 0.5 m to 20 m size, such as that sold by Cabot under the trade mark Cab-O-Sil MS-75D. The silica is pretreated with an oligomeric organopolysiloxane, containing vinylmethylsiloxane unit and silanol terminal groups. [0178] iii) Si-rubber base 2 is an uncatalysed Silicone Rubber Base of 40 Shore A hardness (measured in accordance with ASTM D2240-03 comprising a blend of organopolysiloxane gums, and silica filler. The blend of gums is a mixture of vinyldimethyl terminated polydimethylsiloxane, vinyldimethyl terminated polydimethyl methylvinyl siloxane copolymer gum and a trimethyl terminated polydimethyl methylvinyl siloxane copolymer. The gum has a specific gravity of 1.11 and blend has a Williams Plasticity number comprised between 150 and 200 mm/100, measured in accordance with ASTM D-926 - 08. [0179] iv) The silica used as reinforcing filler is a fumed (pyrogenic) silica with a particle size comprised in the range of 0.5 m to 20 m size, such as that sold by Cabot under the trade mark Cab-O-Sil MS-75D. The silica is pretreated with an oligomeric organopolysiloxane, containing vinylmethylsiloxane unit and silanol terminal groups. [0180] v) The Platinum catalyst used in the examples was DowSil Syl-Off 4000 catalyst from the Dow Chemical Company, Midland Mich. [0181] vi) The cross-linker used in the examples was DowSil Syl-Off 7678 Crosslinker, from the Dow Chemical Company, Midland, Mich. [0182] vii) The ethylene acrylate copolymer used was Elvaloy AC 1609 from Dupont which has a co-monomer content of 9wt %, an MFI of 6 g/10 (190 C./2,16 kg), a density of 0.93, a vicat softening point of 70 C. and a melting temperature of 101 C. [0183] viii) The anti-oxidant used was Irganox 1010 from BASF, a sterically hindered phenolic antioxidant.

[0184] The composition utilised are depicted in Table 1.

TABLE-US-00001 TABLE 1 Si-MB 1 Si-MB 2 Si-MB 3 Si-MB 4 Si-Rubber 1 48.246 50 (wt. %) Si-Rubber 2 48.847 50 (wt. %) Pt catalyst 0.257 0.243 (wt. %) SiH cross 1.497 0.91 linker (wt. %) Thermoplastic 49.9 49.9 49.9 49.9 phase (wt. %) Anti-oxidant 0.1 0.1 0.1 0.1 (wt. %)

[0185] The mixing of components and the silicone vulcanization reaction was carried out using a twin screw extruder, 25 mm of diameter and 48 L/D. The twin screw extruder processing barrel sections were heated up in a range from 160 C. up to 180 C. (from 180 C. up to 200 C. at the die). The ethylene acrylate copolymer was fed into the main extruder entry port and melted as it passed through the extruder. Downstream, the silicone base, platinum catalyst and SiH crosslinker were individually introduced into the melted ethylene acrylate copolymer to ensure even distribution and dynamic vulcanization reaction of the silicone base to form a silicone elastomer in the melted ethylene acrylate copolymer. The location of each individual injection port is set in order to ensure the silicone vulcanization reaction is completed within the residence time of the ethylene acrylate copolymer in the extruder. In the case of examples using uncured silicone base rubber, the platinum catalyst and SiH cross linker were not introduced into the extruder. The resulting product was pelletized.

[0186] The resulting pelletized masterbatch product was dried at 110 C. for 2 hours to reach a max relative humidity by 0.02%.

[0187] The resulting silicone masterbatches in pellet form were then dry blended at the required ratio together with a 70% by weight polycarbonate (PC) and 30% by weight acrylontrile butadiene styrene (ABS) thermoplastic blend sold under the name of Bayblend T85XF from Covestro AG of Leverkusen, Germany and compounded through a melt mixing process using a co-rotating twin screw extruder with the characteristic's D20 and L/D 40. The processing temperature are set between 230 and 250 C. with a screw speed of 200rpm and a throughput of 2.5kg's/hour. The PC/ABS blend had also been pre-dried at 110 C. for 3 hours to reach a max relative humidity by 0.02% prior to introduction in the extruder.

[0188] The above were compared with four Comparative materials: [0189] COMP-1: An unmodified PC/ABS (30% ABS)the material modified in the examples by introduction of the masterbatches described above. COMP-1 is used as a reference or base-line. The COMP-1 material was dried for 3 hours at 110 C. prior to injection moulding. [0190] COMP-2: Hushlloy HS-210a commercially available anti-squeaking PC-ABS grade from Techno Polymer Co Limited. it is understood that this is a chemically modified ready to use PC/ABS based on copolymerization technologies which provides anti stick-slip/anti-squeaking behaviour by delivering a high stick behaviour to prevent parts moving from each other. [0191] COMP-3: Molykote D96 UV anti friction coating a fluoro based UV-curable anti-squeaking coating. This water based coating contains 42% of PTFE. This coating is an Anti-noise, Anti-friction Coating for automotive industry (interior application) that can be sprayed or brushed. Perfluoro based coatings are best in class solution for anti-squeaking. The anti-squeaking process is delivered by dramatically decreasing static and dynamic coefficient of friction of the coated part against its counter-part. Plates of PC/ABS (30% by weight ABS) material were first cleaned with L-13 cleaner and then coated with a layer of the anti-friction coating with a thickness of approximately 20 m. Plates were put in oven for a period of 5 minutes at 50 C. and cured under UV. [0192] COMP-4: a compounded PC/ABS in which a trimethyl siloxy terminated polydimethylsiloxane (PDMS) with a kinematic viscosity at 25 C. of 1000 mm.sup.2.Math.s.sup.1 (cSt) (measured as per ASTM D445-17a) was prepared with a 2wt % loading of the PDMS. The material was prepared by twin screw extrusion process using liquid injection. The material was dried for 3 hours at 110 C. prior to injection moulding. PDMS is a well-known and highly efficient lubricant which has been used to minimise the squeaking noise with respect to some thermoplastic materials. However, it could be seen that the PDMS used was not very compatible with PC/ABS thermoplastic material being used in the examplessignificant bleeding was observed upon injection and the surface of injection moulded parts were not homogenous and non-aesthetic with a strong oily feeling and aspect. It was also noticed that the PDMS was washed out with time as non-embedded in the host matrix.

[0193] Once prepared as described above the examples materials and comparative materials were injection moulded, typical injection temperatures were between 230-250 C., using a back pressure of 150bar (15000000 Nm.sup.2), an injection speed of 0.35 m/s and a mould temperature of 70 C.

Stick-Slip/Squeaking Evaluations:

[0194] Squeak test was performed on an SSP04 Stick-slip test bench from Ziegler Instruments GmbH following VDA 230-206: 2007 (Examination of the stick-slip behaviour of Material Pairs Part 1 to 3) in which a flat sample plate of an injection moulded example/counter example under test (dimensions of 1001004 mm) was slid across a flat rectangular piece of non-modified injection moulded PC/ABS (dimensions 2550 mm) using the test parameters indicated as follows in Table 2:

TABLE-US-00002 TABLE 2 Temperature 23 (+2 C.) Relative Humidity 50% (+5%) Moving Plates 25 50 mm Speed 4 mm/s Load 40 N Movements/cycle (back and forth) 4050 Length/movement 5 mm

[0195] The SSPO4 Stick-slip test bench provides several results from the practical assessment:

[0196] The Risk Priority Number or RPN provides a number which gives the probability of a pair of materials giving an audible squeaking noise in accordance with VDA 230-206: 2007 (ASTM 230-206). An RPN between 1 and 3 identifies material pairs with no or minimal squeaking risk. An RPN of from 4 to 5 represents grades where no squeaking is registered but the material pair may deliver squeaking on a long term. Finally grades above 5 i.e. between 5 and 10 identify material pairs delivering audible squeaking noise.

[0197] The impulse value provides the number of stick-slip occurrences between the 2 surfaces (start-stop) during the test. Anti-squeaking additives are targeting the lower impulse values. Maximum Acceleration: acceleration recorded during the restart phases of each stick-slip phenomenon. The high the Max. Acceleration is, the worst the stick-slip phenomenon will be and the higher the risk of noise generation will be.

[0198] Static coefficient of friction (SCOF) is defined as the longitudinal force to be applied in parallel to the displacement to induce the movement.

[0199] Dynamic coefficient of friction (DCOF) is defined as the longitudinal force needed to keep one surface moving against the other with a constant speed.

[0200] The surface appearance by visual inspection of the test samples were graded as good (no visible traces of products demix or flow marks), poor (Visible flow marks) or bloom (product demixing with surface flow marks and non-homogeneity). The examples and counter examples were also visually studied for evidence of Surface abrasion (surface damage and scratches) after stick-slip test and of course it was noted if/when any audible noise was identified during the test procedure.

[0201] All results will be expressed as the mean average of the 3 independent samples on which 10 cycles (405 movements back and forth/cycle; total of 4050 movements) have been performed. The unmodified PC/ABS went through the same processing sequences (extrusion and injection moulding) as the test samples to follow the same thermic history. Comp 3, the commercial ready to use PC/ABS was directly injected into the testing moulds. The compounded materials were prepared including 4% by weight of masterbatch or in the case of Comp 4, PDMS as indicated in Table 3 below.

[0202] The compounded formulations utilised for the testing are listed as in Table 3 below:

TABLE-US-00003 TABLE 3 In wt % Ex-1 Ex-2 Ex-3 Ex-4 COMP-4 PC/ABS 96 96 96 96 98 Si-MB-1 4 Si-MB-2 4 Si-MB-3 4 Si-MB-4 4 PDMS (1000 2 mm.sup.2 .Math. s.sup.-1 Comments X-linked X-linked Non Non 1000 high shore low shore X-linked X-linked mm.sup.2 .Math. s.sup.-1 Si-base Si-base high shore low shore Silicone Si-MB Si-MB Si-base Si-base oil Si-MB Si-MB

[0203] In the examples herein Ex-1 and Ex-2 exemplified the vulcanized silicone masterbatches and Ex-3 and Ex-4 are their non vulcanized counter parts.

Experiment 1

[0204] This was performed to show that the product from the present invention and presented under Ex-1 is working in the same way under comparable conditions to the current benchmark product and technical approaches exemplified by ComEx-2 and ComEx-3.

TABLE-US-00004 TABLE 4 Values (Std dev) Ex-1 CompEx-1 CompEx-2 CompEx-3 Surface Good Good Good Good appearance* RPN** 1.2 (0.3) 9.7 (1.1) 1.1 (0.2) 1.1 (0.14) Max 0.14 (0.15) 6.4 (1.3) 0.13 (0.04) 0.08 (0.05) acceleration (g) Impulse 327 (91) 14800 (2500) 78 (96) 516 (51) (counts) Static 0.18 (0.02) 0.41 (0.03) 0.34 (0.04) 0.1 (0.001) COF Dynamic 0.17 (0.02) 0.35 (0.02) 0.3 (0.02) 0.09 (0.001) COF Surface Very Light Very high Light Very Light abrasion visible?* Audible No Yes No No noise generation

[0205] As anticipated the non-modified PC/ABS CompEx-1 had a very high RPN classification, the highest values for both static and dynamic coefficient of friction (COF) as well as a high frequency of stick-slip occurrences indicated by the impulse value, 14800 and a Max Acceleration at 6.4. The surface of the CompEx-1 sample under test could be seen to have significant abrasion damage which to an extent resulted in the presence of polymeric powder on the surface after being tested due to the surface abrasion. Finally, it generated audible noises during the test.

[0206] The best in class benchmarking CompEx-3 shows excellent results. The coating is delivering anti-squeak performance by delivering a very low COF between the material pairs. A very low RPN was identified (close to 1 in average), together with providing the lowest static and dynamic COF results, respectively at 0.1 and 0.09. The impulse rate was 516 together which together with a low Max acceleration of 0.08 contributes also to absence of noise generation.

[0207] CompEX-2, the commercial ready to use modified PC/ABS compound, delivered good stick-slip performances with no stick-slip development. However, this compound did show high COF values, close to the original PC/ABS matrix which could pose some issues in typical applications where a good gliding effect would be required.

[0208] Ex-1, the result of compounding a thermoplastic silicone vulcanisate masterbatch into the PC/ABS has an excellent RPN value at 1.2, comparable to CompEx-2 and CompEx-3 and well below the maximum acceptable RPN value tolerated of 3. Ex-1 as hereinbefore described has performance values comparable to CompEx-2 with slightly lower impulse and COF values, making it more suitable in our view than CompEx-2 being closer results wise to said CompEx-3 considered to be best in class.

Experiment Part 2

[0209] A second series of trials was performed looking at broader scope.

TABLE-US-00005 TABLE 5 Values Comp Comp Comp Comp (Sdt dev) Ex-1 Ex-2 Ex-3 Ex-4 Ex-1 Ex-2 Ex-3 Ex-4 Surface Very Very Good Not Good Good Good Bloom** appearance Good Good Good RPN 2.4 2 4.3 2.3 9.7 1.1 1 2.8 (0.64) (0.2) (1.1) (0.6) (1.1) (0.21) (0.1) (1.6) Max 0.58 0.26 1.53 0.5 6.4 0.1 0.1* 0.72 acceleration (0.25) (0.1) (1.21) (0.3) (1.3) (0.01) (0.02) (0.56) (g) Impulse 784 933 4292 613 14800 135 0* 1030 (counts) (256) (114) (1816) (347) (2500) (61) (282) SCOF 0.2 0.19 0.21 0.12 0.41 0.2 Not 0.06 (0.01) (0.04) (0.03) (0.03) (0.03) (0.01) measured* (0.008) DCOF 0.18 0.17 0.18 0.1 0.35 0.1 0.1* 0.05 (0.01) (0.03) (0.03) (0.03) (0.02) (0.01) (0.003) (0.0075) Surface Very Very Light Not Very Light Very Light abrasion light light visible high Light visible? Audible No No No No Yes No No No noise generation *ComEx-3: Material not gliding against each other upon testing. As such, Impulse is 0 and Static and Dynamic COF as well as Max acceleration are not representative values from the testing. **surface aspect heavily impacted due to surface swelling of the PDMS.

[0210] Ex-1 and Ex-2 are respectively the crosslinked Si-MB's containing a high and low shore-A base gum. Ex-3 and Ex-4 are the corresponding non cross-linked Si-MB's of the high and low shore A base gum. It has been interesting to discover that cross linking is required for high shore A based gum Si-MB' s in order to deliver anti-squeaking performances. Indeed, the non cross-linked high shore A silicone based Si-MB, represented by Ex-3, did not show acceptable anti-squeaking performances as a RPN of 4.3 was obtained, together with higher impulse and Max acceleration. As such, this Ex-3 is not fulfilling the requirement of the present invention as it clearly showed RPN numbers above limits of 3, which is the limit defined by VDA 230-206 to consider a material pair as anti-squeaking.

[0211] On the contrary, the low shore silicone base Si-MB showed good anti-squeaking performances both for the cross-linked and the non cross-linked additive, represented respectively by Ex-2 and Ex-4. However, surface aspect is dramatically improved by the cross-linking process as Ex-2 did show excellent surface aspect while Ex-4 did not show good surface aspect.

[0212] As expected Comp-Ex4 showed some anti-squeaking performance with an RPN in an average at the limit value of 2.8. The bad dispersion of PDMS and surface inhomogeneity is exemplified by the high standard variation measured on the RPN number, showing a low repeatability of the measurement. On the other side, surface was heavily impacted by PDMS blooming upon injection. Surface is very greasy and non-aesthetics, making it not suitable for automotive visible parts applications. On top, PDMS are liquids making them not used friendly. This is where Ex1, 2 and 4 from present invention are delivering very good anti-squeaking performances with excellent surface aspect while being easier to use (pellets).