WO1999054402A1

WO1999054402A1 - Process for the preparation of a polyvinylarene composition and polyvinylarene compositions

Info

Publication number: WO1999054402A1
Application number: PCT/EP1999/002759
Authority: WO
Inventors: Josephina Cornelia Maria Brokken-Zijp; Sophie Simone Lucie Rubbers; Johannes Carolus Maria Gillemans; Michael Vermaat; Liane Michelle Simone Schoonus
Original assignee: Nova Chemicals (International) S.A.
Priority date: 1998-04-20
Filing date: 1999-04-19
Publication date: 1999-10-28
Also published as: AU3821999A

Abstract

Process for the preparation of a vinylarene polymer-containing composition, which process comprises admixing a hydrogenated block copolymer of a vinylarene and a conjugated diene with a polymer composition containing an ethylene-propylene-diene (EPDM) rubber in a matrix of polyvinylarene, with the proviso, that if the hydrogenated block copolymer is a radial teleblock copolymer, the composition does not comprise polyphenylene ether. Vinylarene polymer-containing composition, comprising a hydrogenated block copolymer of a vinylarene and a conjugated diene, and a polyvinylarene which in a matrix comprises an EPDM rubber, and, optionally, a second polyvinylarene and/or an extender oil.

Description

- 1 -

PROCESS FOR THE PREPARATION OF A POLYVINYLARENE COMPOSITION AND POLYVINYLARENE COMPOSITIONS

The present invention relates to a process for the preparation of a vinylarene polymer-containing composition, and to vinylarene polymer-containing compositions. Vinylarene throughout the application means an aromatic compound to which at least one vinyl group is attached.

Compositions containing polyvinylarene and ethyiene- propylene diene (EPDM) rubbers have the advantage that tney have improved impact resistance vis-a-vis the polyvinylarene per se . However, it has been found that the presence of EPDM rubber reduces the gloss of the final product. This makes EPDM-containing compositions less suitable for certain applications.

The issue of providing impact resistant polymer of a vinylarene with a smooth surface (lustre) has been addressed m JP-A 1/190 741. Thereto, EPDM rubber, polystyrene and a di-block copolymer are added togetner and extruded. Although the application does not give any proof that the lustre is improved, the present Applicant has found that the gloss improvement indeed occurred.

However, the extrudates prepared in accordance with this Japanese application showed an unacceptably low impact strengt .

The object of the present invention is to improve the gloss of a blend of polyvinylarene and EPDM rubber whilst ensuring that the impact strength would be acceptably high. Surprisingly, it was found that a composition containing polyvinylarene and EPDM rubber having improved gloss and retaining a high impact strength can be obtained by a process in which a hydrogenated block - 2 - copolymer of a vinylarene and a conjugated diene is added to a polyvinylarene that has been modified by the inclusion of EPDM rubber during the polymerisation reaction of the vinylarene monomer. The effect is the more surprising now that the hydrogenated block copolymer should not be added at the start of the polymerisation reaction but when there is a matrix of polyvinylarene containing the EPDM rubber.

US-A 4 139 574 describes compositions of polyphenylene ethers which include a polyvinylarene, such as polystyrene, modified with an EPDM rubber, and a radial teleblock copolymer. The modification of the polyvinylarene by the EPDM rubber has been accomplished by dissolving the EPDM rubber in the monomer of the vinylarene and subsequent polymerisation. The teleblock copolymer is added in a later stage with the polyphenylene ether. The object of the composition thus obtained is the provision of an improved impact resistance. There is no indication that the addition of a block copolymer to an EPDM rubber-modified polyvinylarene has any effect on the gloss properties of the resulting composition. As indicated, the object of the present invention is the provision of a polyvinylarene composition with an improved gloss. Accordingly, the present invention provides a process for the preparation of a vinylarene polymer-containing composition, which process comprises admixing a hydrogenated block copolymer of a vinylarene and a conjugated diene with a polymer composition containing an ethylene-propylene-diene (EPDM) rubber m a matrix of polyvinylarene, with the proviso, that if the hydrogenated block copolymer is a radial teleblock copolymer, the composition does not comprise polyphenylene ether. In this specification the term "EPDM rubber-modified polyvinylarene" will be used to indicate - 3 - a polyvinylarene that contains an EPDM rubber in a polyvinylarene matrix.

The admixing of the hydrogenated block copolymer can be achieved m a number of ways. It is important that the admixing is done to a composition wherein the EPDM rubber is already incorporated into a matrix of polyvinylarene. Hence, it could be that the EPDM rubber-containing composition has been polymerised completely. It is then convenient to prepare a premix of an EPDM rubber-modified polyvinylarene and the block copolymer, and melt the premix. Subsequently, the molten premix is suitably extruded, and the extrudate is cooled. The result is an extrudate that can be easily subjected to, e.g., injection moulding, and which then yields a glossy moulded article with a high impact strength.

EPDM rubber-modified polyvinylarene is usually prepared by dissolving the EPDM rubber in the vinylarene monomer and polymerise the monomer to some extent, suitably to a polymerisation degree of 10-40% based on the vinylarene monomer. This is the so-called pre- polymeπsatio . This way the EPDM rubber is incorporated into a matrix of polyvinylarene. The pre-polymerisation product is subsequently suspended m an aqueous phase and the remaining vinylarene monomer is polymerised to completion. After the completion of the polymerisation, the hydrogenated block copolymer is suitably added to the polyvinylarene product.

The expert skilled m the art will realise that the polymerisation of the EPDM rubber-containing solution of vinylarene monomer can be carried out using conventional methods, e.g. those described in GB-A 2 074 174 or US-A 4 469 847. The initial polymerisation may be conducted in the absence of an initiator, the polymerisation being purely thermal. Another, more preferred, method is to carry out the initial - 4 -

polymerisation in the presence of a free-radical initiator. Suitable initiators include azo and peroxy compounds, such as di-t-butyl peroxide, lauroyl peroxide, cumyl hydroperoxide, azobisisobutyronitπle, or mixtures thereof. The amount of initiator is generally from 0.01 to 2 %wt, based on the amount of EPDM rubber and vinylarene monomer. The temperature is suitably from 75 to 125 °C. It may be advantageous to add chain transfer agents to the mixture, such as halogenated compounds, dimer of α-methylstyrene, or preferably mercaptans like t-dodecyl mercaptan or n-dodecyl mercaptan. Suitable amounts of such chain transfer agents range from 0.001 to 1 %wt, based on the weight of EPDM rubber and vinylarene monomer. After 10 to 40% conversion of the vinylarene monomer there is a phase inversion as described in

GB-A 2 074 174 and US-A 4 469 847. Subsequent to the pre-polymeπsation the reaction product is subjected to suspension polymerisation.

In the suspension polymerisation step the reaction product can be suspended n an aqueous medium, suitably at a temperature of from 10 to 80 °C, and at a volume ratio of organic phase to aqueous phase in the range of from 1:3 to 4:3.

Suspending agents which can be used in the present process are poly (vinyl alcohol), gelatine, agar, sodium salt of polyacrylic acid and polymethacrylic acid, polyethylene glycol, hydroxyethyl or hydroxymethyl cellulose, carboxy methyl cellulose, methyl cellulose, polyvinyl pyrrolidone, polyacrylamide, copolymer of styrene and maleic anhydride, preferably m a molar ratio of between 2:1 and 1:2, ethylene glycol or combinations tnereof. Further, it is possible to use inorganic suspension stabilisers such as alumina, magnesium silicate or phosphates, like tricalcium phosphate and/or alkali metal (hydrogen) phosphates, optionally in - 5 - combination with any of the polymeric compounds mentioned earlier .

The suspension polymerisation step is suitably carried out thermally or m the presence of initiators . It is preferred that this polymerisation is carried out with the help of conventional initiators. In particular in an amount of 0.01-2 %wt , based on the total amount of vinylarene. Such initiators are tert. -butyl peroxy benzoate, 1, 1-bιs ( tert . -butylperoxy) 3, 3, 5-tπmethyl- cyclohexane, 1, 1-bιs (tert . -butyl peroxy) cyclohexane, tert . -amylperoxy-2-ethylhexyl carbonate, tert. -butyl peroxy-2-ethylhexyl carbonate, tert. -butyl peroxy- 3, 5, 5-tπmethyl hexanoate, tert . -butyl peroxy isopropyl carbonate, tert . -butylperoxy acetate, 2,2-bιs (tert.- butyl peroxy) butane and tert. -butyl peroxy stearyl carbonate, dicumyl peroxide or combinations thereof. Preferably, initiators are used which do not generate benzene. The polymerisation may be carried out at more than one temperature level. The temperature ranges from 80 and 150 °C. The person skilled in the art will realise that at different temperature levels different initiators may be used m accordance with the half-lives of the initiators .

Suitable vinylarene monomers for use m the process may be selected from styrene, α-methyl-styrene, chloro styrene, dimethylstyrene and styrenic derivatives such as vmyltoluene . Preferably, the vinylarene is styrene, optionally mixed with at most 10 %wt of any other vinylarene, based on total amount of vinylarene. The compositions according to the present invention contain an EPDM rubber. By EPDM rubber is understood a terpolymer of ethylene, propylene and a diene. Examples of EPDM rubbers suitable for use in the present compositions include as termonomer a non-conjugated diene compound, such as 1, 4-hexadιene, 2-methyl-l, 5-hexadιene, - 6 - dicyclopentadiene, ethylidene norbornene, 1,4-cyclo- heptadiene, 1, 5-cyclooctadιene and mixtures thereof. Suitable EPDM rubbers comprise 10-90 %wt ethylene, 10-90 %wt propylene and 0.1-12 %wt, preferably 2-10 %wt diene. The EPDM rubber to be preferably applied is also characterised by a Mooney viscosity (ML (1+4) 125 °C) in the range of from 20 to 80.

The amount of EPDM rubber present m the composition is preferably between 3 and 50 %wt, more preferably from 5 to 20 %wt, based on the total of EPDM rubber and polyvinylarene .

The hydrogenated block copolymer of a vinylarene and a conjugated diene is suitably present in the process according to the present invention in a range of 0.5 to 20 %wt, based on the weight of block copolymer, EPDM rubber and polyvinylarene. Although it is not attractive from an economical point of view, relatively large amounts of block copolymer can be present in the composition. The vinylarene in the block copolymer is suitably styrene, although minor amounts of other unsaturated compounds such as polycyclic non-conjugated dienes, or those described above, can also be used. A minor amount could be up to 20% by weight, based on total weight of the polyvinylarene block, preferably less than 10% by weight, more preferably less than 5% by weight, most preferably less than 1% by weight. The conjugated diene that has been used can be selected from the group consisting of butadiene, isoprene, 2 , 3-dιmethyl-l , 3 butadiene, 1, 3-pentadιene, and 3-butyl-l, 3-octadιene, isoprene and butadiene being preferred. It will be appreciated that the preparation of these block copolymers is known in the art. Also the hydrogenation of the block copolymers has been disclosed extensively. An example of such disclosures is in US-A 3 696 088. After the hydrogenation a minimal residual unsaturation may - 7 - remain. The residual unsaturation is advantageously less than 0.2%, based on the original unsaturation.

The hydrogenated block copolymers may be radial or linear. Preferably the block copolymers are linear, more preferably, they are linear di-and/or triblock copolymers. In a diblock copolymer one block consists of a polymer of vinylarene (e.g. polystyrene) . The other block is a hydrogenated polydiene block (e.g., hydrogenated polybutadiene or polyisoprene) . In a triblock copolymer a block of hydrogenated polydiene is connected on either end to a block of vinylarene. A linear block copolymer can be represented schematically by an A-B diblock or A-B-A triblock, herein A represents a vinylarene polymer block and B represents a hydro- genated diene polymer block. When butadiene is used as conjugated diene, the hydrogenated block will consist of an ethylene/butylene copolymer; whereas when isoprene has been used, the resulting block will consist of ethylene/propylene copolymer. It was found that compositions having an especially high gloss and good impact resistance, have been obtained with the help of hydrogenated block copolymers containing between 10 and 40% by weight of vinylarene, based on total amount of vinylarene and hydrogenated diene, and having a weight average molecular weight of between

40,000 to 500,000, in particular from 75,000 to 300,000 as measured in accordance with gel permeation chromatography based on polystyrene calibration.

The linear block copolymer most preferably applied, can consist of mixtures of diblock and tri-block copolymers. If such mixtures are used the tri-block copolymers are suitably present in an amount of 50 to 80 %wt, based on total amount of di- and triblock copolymers . - 8 -

The present invention also provides compositions of vinylarene polymers, EPDM rubber and a hydrogenated block copolymer. Accordingly, the present invention provides vinylarene polymer-containing compositions, comprising a hydrogenated block copolymer of a vinylarene and a conjugated diene, and a polyvinylarene which m a matrix comprises an EPDM rubber, with the proviso, that if the hydrogenated block copolymer is a radial teleblock copolymer, the composition does not comprise poly- phenylene ether. This composition is obtainable by a process which comprises admixing the hydrogenated block copolymer of a vinylarene and a conjugated diene with a polymer composition containing an EPDM rubber in a matrix of polyvinylarene, with the proviso, that if the hydrogenated block copolymer is a radial teleblock copolymer, the composition does not comprise polyphenylene ether.

As already indicated, the hydrogenated block copolymer is preferably a linear block copolymer. Accordingly, the present invention further provides vinylarene polymer-containing compositions, comprising a linear hydrogenated block copolymer of a vinylarene and a conjugated diene, and a polyvinylarene which m a matrix comprises an EPDM rubber, which composition is obtainable by admixing the linear hydrogenated block copolymer of a vinylarene and a conjugated diene with a polymer composition containing an EPDM rubber in a matrix of polyvinylarene .

The properties of the compositions according to the present invention are so advantageous that they can be used to improve the gloss properties of other polymers. In particular, they can be used in the gloss improvement of other polyvmylarenes, such as polystyrene. Accordingly, the present invention also relates to vinylarene polymer-containing compositions, comprising a - 9 - hydrogenated block copolymer of a vinylarene and a conjugated diene, and a polyvinylarene which in a matrix comprises an EPDM rubber, and a second polyvinylarene. When a second polyvinylarene is present the amount thereof may vary between wide ranges, depending on the desired optimisation of the properties. Advantageously, the amount of second polyvinylarene is from 10 to 200 pbw per 100 pbw of the total of EPDM rubber and polyvinylarene matrix. The second polyvinylarene has suitably a Mw of between 70,000 to 500,000, and a melt flow rate (DIN 53735 - at 200 °C, 5kg) of 0.5 to 50 cc/10 min.

Further, the compositions according to the present invention may contain conventional additives . Surprisingly, it has been found that the presence of antioxidants and ultraviolet absorbers is especially advantageous in that they further improve the gloss of the composition. Other suitable additives include flame retardants (such as halogenated hydrocarbons), pigments, mineral fillers (such as silicates or glass fibres) . Very suitably the compositions contain extender oils. These extender oils suitably have a density at 15 °C

(DIN 51757) in the range of 0.8 to 0.95 kg/m³, and a kinematic viscosity at 40 °C (DIN 51562) in the range of

70 to 120 cSt. The oil may be present in an amount up to 10 %wt, based on the total of EPDM rubber, hydrogenated block copolymer and polyvinylarene, suitably from 0.5 to

5 %wt.

The compositions obtained and obtainable according to the present invention can be processed further by methods such as screw extrusion, thermoforming and injection moulding .

The invention will be elucidated by means of the following examples. 10

EXAMPLE 1

In a conventional manner, substantially as described in example 4 of US-A 4,469,847, two batches of EPDM-modified polystyrene were prepared. The EPDM rubber used is characterised by a Mooney viscosity [(1+4) 125 °C] of 33 and contained 50 %wt ethylene, 46 %wt propylene and 4 %wt ethylidene norbornene . The result is that the EPDM rubber is incorporated into a matrix of polystyrene. Batch 1 of the polystyrene obtained is designated PSI. It contained 11.5 %wt of EPDM rubber. The polystyrene product obtained in batch 2 is designated PS2. This product contained 11.5 %wt EPDM rubber, too. The Charpy impact strength of the EPDM-modified polystyrene (DIN 53453) at 23 °C was 9 mJ/mm² for PSI and

14 mJ/mm² for PS2.

The EPDM rubber-modified polystyrene was mixed with hydrogenated polystyrene/polybutadiene or polystyrene/ polyisoprene block copolymers with the characteristics as described in Table 1 below.

TABLE 1

Block Mw Polystyrene polybutadiene diblock/ copoly(xlOOO) * block(s) %wt (PB)/ triblock mer polyisoprene (PI)

A 123 37 PI di

B 180 28 PI di

C 100 30 PB tri

D 270 30 PB tri

E 140 13 30/70 wt/wt Pl-di PI/PB mixture and PB- tri

based on polystyrene calibration - 11 -

In a number of experiments the EPDM rubber-modified polystyrene was mixed with one or more of the block copolymers in the quantities as indicated in Table 2, and extruded. During extrusion conventional antioxidant and ultraviolet stabilisers were added. The extrudates obtained were injection moulded to yield specimens for impact and gloss measurements. The Charpy impact measurements were conducted in accordance with DIN 53453 at a temperature of 23 °C . The mean value of 5 measurements is shown in Table 2. The gloss measurements were made in accordance with ASTM D523-85.

The minimum sample size used was 50x100 mm². The mean value of 4 or 5 measurements are given. The higher the figure mentioned, the better the gloss properties are. The results are shown in Table 2.

TABLE 2

ExperiPSI or PS2 Block Impact, Gloss, Gloss, ment %wt copolymer, mJ/mm² 20° 60° No. %wt

1 PSI 100 - 0 9 39 87

2 PSI 95 A 5 8 49 92

3 PSI 95 B 5 8 48 90

4 PSI 95 C 5 12 42 88

5 PSI 95 E 5 14 52 95

6 PS2 100 - 0 14 28 83

7 PS2 98 B 2 15 36 86

8 PS2 97 B 3 15 40 88

9 PS2 95 B 5 16 42 90

10 PS2 93 B 7 16 47 92

11 PS2 90 B 10 16 54 93

Experiments 1 to 5 clearly show that the addition of various di- or triblock copolymers leads to improved gloss whilst at least maintaining an acceptable impact - 12 - strength. In many cases an enhanced impact strength was found. It appears that the use of hydrogenated polybutadiene-containmg block copolymer has a favourable effect on the impact. Also the block copolymer preferably consists at least partly of triblock copolymer. The results of Experiment Nos . 6 to 11 show that at increasing amounts of block copolymer, the gloss improves, whereas the impact strength first increases and subsequently reaches a constant level. EXAMPLE 2

In order to show that the invention also works when the compositions contain an extender oil and/or another polymer, a number of experiments were conducted m which the final compositions contained a white oil with a density (at 15 °C) of 0.87 (DIN 51757) and a kinematic viscosity (at 40 °C, according to DIN 51562) of 94 cSt, and a polystyrene. PSI was tested with a polystyrene which had a Mw of 300,000, and a melt volume flow rate (DIN 53735) (at 200 °C, 5 kg) of 4 cc/10 mm. PS2 was mixed with a polystyrene having the following characteristics; a Mw of 200,000 and a melt volume flow rate of 8 cc/10 mm (DIN 51562, 200 °C, 5 kg) . These compounds were added to the mixture before the extrusion. The same parameters as indicated in Table 2 have been measured. Results are shown Table 3.

13 -

TABLE 3

Exp. EPDM mod. Block Oil Poly Impact Gloss Gloss No. Polycopopbw stymJ/mm² 20° 60° styrene lymer rene pbw pbw pbw

6 PS2 100 - 0 0 0 14 28 83

12 PS2 52.5 D 5 2.5 40 14 40 90

1 PSI 100 - 0 0 0 9 39 87

13 PSI 92.5 D 5 2.5 0 15 43 88

14 PSI 95.5 B 3 1.5 0 10 53 93

15 PSI 52.5 D 5 2.5 40 9 70 93

Table 3 clearly shows that the addition of extender oil to the mixture of EPDM rubber-modified polystyrene and block copolymer at least maintains impact and yields higher gloss. Comparison between the results of experiments 6 and 12, and 1 and 15, respectively, shows that whilst the impact is retained the addition of low- cost polystyrene to the mixture of EPDM rubber-modified polystyrene and block copolymer yields an significant improvement m the gloss of the moulded article. COMPARATIVE EXAMPLE

In order to compare the compositions according to the present invention with the compositions according to JP-A 1/190 741. An experiment was conducted in which as separate components an EPDM rubber, a block copolymer and a polystyrene were blended and subsequently extruded. The Japanese document teaches that the block copolymer must be a diblock with an average molecular weight of at least 10,000 and containing 30 to 60 %wt of styrene and 40-70 %wt of hydrogenated diene.

75 Parts by weight of the polystyrene described in Example 2 was mixed with the EPDM rubber described m - 14 -

Example 1 and with diblock copolymer A, fulfilling the requirements of the teachings of the Japanese document. The mixture was extruded and the extrudates were subjected to injection moulding. From the moulded specimens impact And gloss were measured as done in the examples. The results were: gloss 20°: 98; gloss

60°: 101; impact 3 mJ/mm².

These results make it clear that the composition obtained has an unacceptably low impact strength.

Claims

- 15 -C L A I M S

1. Process for the preparation of a vinylarene polymer- containing composition, which process comprises admixing a hydrogenated block copolymer of a vinylarene and a conjugated diene with a polymer composition containing an ethylene-propylene-diene (EPDM) rubber in a matrix of polyvinylarene, with the proviso, that if the hydrogenated block copolymer is a radial teleblock copolymer, the composition does not comprise polyphenylene ether.

2. Process according to claim 1, in which the admixing is carried out by preparing a premix of a polyvinylarene which has been modified by an EPDM rubber, and the block copolymer, and melting the premix.

3. Process according to claim 2, in which the molten premix is extruded, and the extrudate is cooled.

4. Process according to any of claims 1-3, in which the vinylarene is styrene.

5. Process according to any one of claims 1-4, in which the amount of EPDM rubber in the composition ranges from 3 to 50 %wt, based on the total of EPDM rubber and polyvinylarene.

6. Process according to any one of claims 1-5, in which the amount of hydrogenated block copolymer ranges from 0.5 to 20 %wt, based on the weight of block copolymer, EPDM rubber and polyvinylarene.

7. Process according to any one of claims 1-6, in which the block copolymer is a linear block copolymer.

8. Process according to claim 7, in which the linear block copolymer is a di- and/or triblock copolymer.

9. Vinylarene polymer-containing composition, comprising a hydrogenated block copolymer of a vinylarene and a conjugated diene, and a polyvinylarene which in a matrix comprises an EPDM rubber, with the proviso, that if the - 1 6 - hydrogenated block copolymer is a radial teleblock copolymer, the composition does not comprise polyphenylene ether.

10. Vinylarene polymer-containing composition, comprising a linear hydrogenated block copolymer of a vinylarene and a conjugated diene, and a polyvinylarene which in a matrix comprises an EPDM rubber, which composition is obtainable by admixing the linear hydrogenated block copolymer of a vinylarene and a conjugated diene with a polymer composition containing an EPDM rubber in a matrix of polyvinylarene.

1_1. Vinylarene polymer-containing composition, comprising a hydrogenated block copolymer of a vinylarene and a conjugated diene, a polyvinylarene which in a matrix comprises an EPDM rubber, and a second polyvinylarene.

12. Composition according to claim 11, in which the amount of second polyvinylarene ranges from 10 to

100 %wt, based on the weight of the hydrogenated block copolymer of a vinylarene and a conjugated diene, and the polyvinylarene which in a matrix comprises an EPDM rubber .

13. Composition according to claim 11 or 12, in which the second polyvinylarene has a melt volume flow rate of 0.5 to 50 ml/10 min.

14. Composition according to any one of claims 9 to 13, which further comprises an extender oil.

15. Composition according to claim 14, in which the extender oil has a density at 15 ┬░C (DIN 51757) in the range of 0.8 to 0.95 kg/m³, and a kinematic viscosity at 40 ┬░C (DIN 51562) in the range of 70 to 120 cSt.