WO2008087675A1

WO2008087675A1 - Styrenic block copolymer plasticised with vegetable oils and process for preparing same

Info

Publication number: WO2008087675A1
Application number: PCT/IT2007/000184
Authority: WO
Inventors: Bruno Cardinali
Original assignee: Tecnocompounds Valtenna S.R.L.
Priority date: 2007-01-19
Filing date: 2007-03-13
Publication date: 2008-07-24
Also published as: ITMC20070010A1

Abstract

The present invention relates to a plastification process of thermoplastic elastomers derived from styrenic block copolymers, in which vegetal oils are used as plastifying substances.

Description

STYRENIC BLOCK COPOLYMER PLASTICISED WITH VEGETABLE OILS AND PROCESS FOR PREPARING SAME

The present invention relates to a plastification process of thermoplastic elastomers derived from styrenic block copolymers, in which vegetal oils are used as. plastifying substances. The present invention also relates to the thermoplastic elastomers obtained with the said process. SBS (Styrene-butadiene-styrene), SIS (styrene-isoprene-styrene), SIBS (styrene-isoprene-butadiene-styrene) block copolymers and hydrogenated derivatives (SEBS, SEPS etc.), are usually plastified with mineral oils of paraffinic type with a low content of aromatic products. When suitably compounded with additives, either organic or inorganic, they are used in many industrial sectors, from footwear to car components, from toys to gaskets.

Being thermoplastic elastomeric materials, they have a considerably advantageous application compared to vulcanised elastomers and therefore they are more and more used, reducing the market share of cross-linked rubbers.

One of the problems of vulcanised elastomeric products is poor biodegradability, since the presence of mineral oils in the products enormously reduces their environmental degradability capacity. Another problem refers to the manufacturing of products that come in contact with the human body: pharmaceutical or oenological vaselines must be used with mineral plastifying agents, with high costs and consequent environmental problems.

The use of organic plastifying agents, such as oils that are extracted from a large variety of vegetal organisms, soya beans, corn, flax, etc., contributes to solve the problems caused by mineral plastifying agents, that is to say human contacts and biodegradability. Many products, such as toys, children shoes, footstraps, slippers that come in direct contact with the skin will find the ideal solution for the human health.

The purpose of the present invention is to overcome the aforementioned problems and inconveniences. This purpose has been achieved with the process claimed in the first claim. The said process consists in a traditional production process of thermoplastic elastomers derived from styrenic block copolymers, which uses for the first time vegetal oils as plastifying substances.

Description of the invention.

Vegetal seed oils are essentially triglycerides of saturated and unsaturated fat acids, therefore in a molecular chain of about 50 carbon atoms there are only

3 ester groups that give a limited general chemical polarity of the product.

The relatively low polarity makes it possible to use the oil as plastifying agent of the paraffinic or paraffinic-olephinic chains between the styrenic blocks of styrene butadiene block or styrene-isoprene block copolymers (or similar products) without migration problems both in production and during product life.

Most of all, no dissolution phenomena of styrenic domains with reduction of general elastomeric characteristics are found; in fact, tension, elongation and elastic return tests have not shown considerable differences with respect to compounds produced with mineral oils.

Thermal resistance tests on samples at 55°C and -25° C have not shown any bleeding of oil products towards the external surface. The production process of compounds based on styrenic block copolymers plastified with vegetal oils perfectly follows the dynamics and logics of the corresponding compounds produced with mineral oils.

Initial absorption process of plastifying agent, addition of fillers of mineral origin (where necessary), addition of various polymer and non-polymer additives, addition of organic pigments and then extrusion with machines that are traditionally used for this type of elastomeric and non-elastomeric materials. EXAMPLE 1

Compound with high content of plastifying agent

Kg

SBS (Europrene SOL T 161 or equivalent ) 100 Colza and soya bean oil 50/50 80

Mix in agitator, slow or fast, for at least 5 minutes, than extrude the mix in a twin screw extruder configured for production of SBS compounds.

Mould the compound in a continuous screw or piston press, producing a specimen with suitable dimensions for physical-mechanical analyses.

The following results were obtained:

Results Method of Result Unit of measurement measurement

Hardness DIN 53505 30 SHORE A

Melt Flow Index DIN 53735 25 g/10' at 190° 5Kg

Tensile strength at DIN 53504 4,5 MPa break

Elongation at break DIN 53504 800 %

Bondability Internal method 6 N/mm

Bleeding Internal method none

Light tightness Internal method Usual as plastified SBS

Mineral OIL

Environmental External exposure Bacterial aggressions and mo stability after a few months

EXAMPLE 2

Kg

SBS (Dynasol 411 or equivalent) 70 SBS (Dynasol 501 or equivalent) 20

Crystal polystyrene 40

Syndiotactic 1 ,2 polybutadiene (RB 840) 40

Vegetal oil (Sunflower, Peanut, Palm mix) 80 parts by weight 35/35/30

Mix in agitator, slow or fast, for at least 5 minutes, than extrude the mix in a twin screw extruder configured for production of SBS compounds. Mould the compound in a continuous screw or piston press, producing a specimen with suitable dimensions for physical-mechanical analyses. The following results were obtained:

Results Method of Result Unit of measurement measurement

Hardness DIN 53505 65 SHORE A

Melt Flow Index DIN 53735 56 g/10' at 190° 5Kg

Tensile strength at DIN 53504 5,0 MPa break

Elongation at break DIN 53504 520 %

Abrasion DIN 53516 190 mm3

Bondability Internal method 8 N/mm

Bleeding Internal method none

Light tightness Internal method Usual as plastified SBS

Mineral OIL

The following results are obtained when comparing the results of these compounds with the corresponding products obtained by replacing vegetal oil with traditional plastifying agent derived from mineral oil: tests

Compound degradation

SEED OIL bacterial aggression

MINERAL OIL non aggression

With reference to mechanical tests, compounds plastified with seed oil have shown the same results of compounds plastified with mineral oil.

Vegetal oils are preferably derived from: peanut, sunflower, flax, corn, soy, colza, sesame, palm, coconut, cashew. Alternatively, the said vegetal oils are derived from vegetal organisms, such as leaves, roots, stems, bark, flowers.

In another alternative solution, the said vegetal oils are derived from a mix of two or more vegetal substances.

It must be noted that the said styrenic block copolymers can be either hydrogenated or non-hydrogenated.

Among non-hydrogenated copolymers, the preferred ones belong to the following groups: SBS (Styrene-Butadiene-Styrene), SIS (Styrene, Isoprene,

Styrene).

Among hydrogenated copolymers, the preferred ones belong to the following groups: SEBS (Styrene, EthyleneButylene-Styrene), SEPS (Styrene-

EthylenePropylene-Styrene), SEEPS (Styrene EthyleneEthylenePropylene-

Styrene).

In a preferred embodiment of the process of the invention, either organic or inorganic substances are added to the said thermoplastic elastomers. Polyethylene polymers and their copolymers, preferably EVA, EBA, EMA,

Polyethylene and derivatives, preferably crystal and/or high impact, polybutadiene, syndiotactic 1 ,2, polyalphametylstyrene are preferred among organic substances.

The following substances are preferred among inorganic substances: talcum, kaolin, calcium carbonate.

Claims

1. Production process of thermoplastic elastomers derived from styrenic block copolymers, consisting in a first mixing stage and a second extrusion stage, characterised in that vegetal oils are used as plastifying substances;

2. process as claimed in claim 1 , characterised in that the said oils are preferably derived from seeds;

3. process as claimed in claim 2, characterised in that the said oils are preferably derived from peanut, sunflower, flax, corn, soya bean, colza, sesame, palm, coconut, cashew;

4. process as claimed in claim 1 , characterised in that the said oils are derived from vegetal organisms, such as leaves, roots, stems, bark, flowers;

5. process as claimed in one or more of above claims, characterised in that the said oils are derived either from a single vegetal substance or from a mix of two or more vegetal substances;

6. process as claimed in one or more of the preceding claims, characterised in that the said styrenic block copolymers are not hydrogenated;

7. process as claimed in above claim, characterised in that the said styrenic block copolymers belong to the following groups: - SBS (Styrene-Butadiene-Styrene)

- SIS (Styrene-Isoprene-Styrene)

8. process as claimed in one or more of claims 1 to 5, characterised in that the said styrenic block copolymers are hydrogenated;

9. process as claimed in above claim, characterised in that the said styrenic block copolymers belong to the following groups:

- SEBS (Styrene-EthyleneButylene-Styrene)

- SEPS (Styrene-EthylenePropylene-Styrene)

- SEEPS (Styrene-EthyleneEthylenePropylene-Styrene)

10. process as claimed in claim 1 , characterised in that mixing is performed in agitator for at least five minutes and extrusion is performed in a twin screw extruder configured for the production of SBS compounds;

11. thermoplastic elastomer derived from styrenic block copolymers obtained with a plastification process as the one described in claims 1 to 10;

12. thermoplastic elastomer as claimed in above claim, characterised in that it is mixed with traditional organic and inorganic additives

13. thermoplastic elastomer as claimed in above claim, characterised in that the said organic additives are Polyethylene polymers and copolymers, preferable EVA, EBA, EMA, Polystyrene and derivatives, preferably crystal and/or high impact, polybutadiene, syndiotactic 1 ,2, polyalphametylstyrene;

14. elastomer as claimed in claim 12, characterised in that the said inorganic additives are preferably talcum, kaolin, calcium carbonate;

15. thermoplastic elastomer as claimed in claim 11 , characterised in that it is obtained by mixing Kg

SBS (Eϋroprene SOL T 161 or equivalent 100

Colza and soya bean oil 50/50 80

16. thermoplastic elastomer as claimed in claim 11 , characterised in that it is obtained by mixing

Kg

SBS (Dynasol 411 or equivalent) 70

SBS (Dynasol 501 or equivalent) 20

Crystal polystyrene 40 Syndiotactic 1 ,2 polybutadiene (RB 840) 40

Vegetal oil (Sunflower, Peanut, Palm mix) 80 parts by weight 35/35/30