THERMOPLASTIC COPOLYMERS WITH A HIGH SULPHUR CONTENT AND PROCESS FOR THE PREPARATION THEREOF

Abstract

A thermoplastic copolymer with a high sulphur content, having sulphur in an amount greater than or equal to 40% by weight, in relation to the total weight of the thermoplastic copolymer with a high sulphur content and at least one monomer having general formula (I):

##STR00001##

wherein: R.sub.1 and R.sub.2, equal or different from each other, represent a hydrogen atom; or R.sub.1 and R.sub.2, may optionally be bound together so as to form, together with the other atoms to which they are bound, a cycloalkene containing from 4 to 6 carbon atoms, saturated, unsaturated, or aromatic, optionally substituted with C.sub.1-C.sub.20 alkyl groups;
the monomer having general formula (I) being present in an amount less than or equal to 60% by weight;
the thermoplastic copolymer with high sulphur content having a complex dynamic viscosity (η*), at 160° C., comprised between 1×10.sup.4 Pa.s and 8×10.sup.6 Pa.s.

Claims

1. A thermoplastic copolymer with a high sulphur content, comprising sulphur in an amount greater than or equal to 40% by weight, in relation to the total weight of said thermoplastic copolymer with a high sulphur content and at least one monomer having general formula (I): ##STR00006## wherein: R.sub.1 and R.sub.2, equal or different from each other, represent a hydrogen atom; or they are selected from C.sub.1-C.sub.20, preferably C.sub.1-C.sub.15, linear or branched alkyl groups, C.sub.2-C.sub.20, preferably C.sub.2-C.sub.15, linear or branched alkenyl groups, C.sub.2-C.sub.20, preferably C.sub.2-C.sub.15, linear or branched alkylidene groups; or R.sub.1 and R.sub.2 may optionally be bound together so as to form, together with the other atoms to which they are bound, a cycloalkene containing from 3 to 6 carbon atoms, saturated, unsaturated, or aromatic, optionally substituted with C.sub.1-C.sub.20 alkyl groups, preferably C.sub.1-C.sub.15, linear or branched, said cycle optionally containing heteroatoms such as, for example, oxygen, sulphur, nitrogen, silicon, phosphorus, selenium; said monomer having general formula (I) being present in an amount less than or equal to 60% by weight, in relation to the total weight of said thermoplastic copolymer with a high sulphur content; said thermoplastic copolymer with a high sulphur content having a complex dynamic viscosity (η*), at 160° C., comprised between 1×10.sup.4 Pa.s and 8×10.sup.6 Pa.s.

2. The thermoplastic copolymer with a high sulphur content according to claim 1, wherein said monomer having general formula (I) is selected from the group consisting of dicyclopentadiene, 5-ethylidene-2-norbornene, 5-vinyl-2-norbornene, and mixtures thereof.

3. The thermoplastic copolymer with a high sulphur content according to claim 1, wherein said thermoplastic copolymer with a high sulphur content comprises sulphur in an amount equal to 50% by weight in relation to the total weight of said thermoplastic copolymer with a high sulphur content and at least one monomer having general formula (I): ##STR00007## wherein R.sub.1 and R.sub.2 are bound together so as to form, together with the other atoms to which they are bound, a cyclopentene, said monomer having general formula (I) being present in an amount equal to 50% by weight in relation to the total weight of said thermoplastic copolymer with a high sulphur content.

4. The thermoplastic copolymer with a high sulphur content according to claim 1, wherein said thermoplastic copolymer with a high sulphur content comprises sulphur in an amount equal to 60% by weight in relation to the total weight of said thermoplastic copolymer with a high sulphur content and at least one monomer having general formula (I): ##STR00008## wherein R.sub.1 and R.sub.2 are bound together so as to form, together with the other atoms to which they are bound, a cyclopentene, said monomer having general formula (I) being present in an amount equal to 40% by weight in relation to the total weight of said thermoplastic copolymer with a high sulphur content.

5. The thermoplastic copolymer with a high sulphur content according to claim 1, wherein said thermoplastic copolymer with a high sulphur content comprises sulphur in an amount equal to 50% by weight in relation to the total weight of said thermoplastic copolymer with a high sulphur content and at least one monomer having general formula (I): ##STR00009## wherein R.sub.1 is hydrogen and R.sub.2 is ethylidene, said monomer having general formula (I) being present in an amount equal to 50% by weight in relation to the total weight of said thermoplastic copolymer with a high sulphur content.

6. The thermoplastic copolymer with a high sulphur content according to claim 1, wherein said thermoplastic copolymer with a high sulphur content has a glass transition temperature (T.sub.g) greater than or equal to 80° C.

7. A method for the preparation of a thermoplastic copolymer with a high sulphur content, the method including the following steps: (i) reacting the sulphur with at least one monomer having general formula (I), in the presence of at least one radical initiator and at least one radical chain terminator, at a temperature comprised between 120° C. and 190° C., for a time comprised between 1 minute and 180 minutes, thus obtaining a liquid pre-polymer, and (ii) pouring the liquid pre-polymer obtained in step (i) into a mould and keep said mould at a temperature comprised between 100° C. and 180° C., for a time comprised between 1 hour and 24 hours, thus obtaining a thermoplastic copolymer with a high sulphur content.

8. The method for the preparation of a thermoplastic copolymer with a high sulphur content according to claim 7, wherein: said radical initiator is selected from the group consisting of mercaptans, such as 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercapto-benzimidazole, 2,5-dimercapto-1,3,4-thiadiazole, 2-mercapto-2,5-dimethylaminopyridine, and mixtures thereof; alkenyl disulphides, such as diallyl disulphide, allyl propyl disulphide, allyl ethyl disulphide, allyl methyl disulphide, or mixtures thereof; and mixtures thereof, said radical initiator is used in said step (i) in an amount lower than or equal to 1% by weight, in relation to the total weight of the reaction mixture (i.e. the mixture of sulphur+monomer+radical initiator+radical chain terminator), and/or said radical chain terminator is selected from the group consisting of aliphatic, cycloaliphatic and aromatic disulphides, such as dimethyl disulphide, diethyl disulphide, dicyclohexyl disulphide, diphenyl disulphide, ditolyl disulphide, or derivatives thereof, and mixtures thereof, and/or said radical chain terminator is used in said step (i) in an amount lower than or equal to 15% by weight, in relation to the total weight of the reaction mixture (i.e. the mixture of sulphur+monomer+radical initiator).

9. The method for the preparation of a thermoplastic copolymer with a high sulphur content according to claim 7, wherein the sulphur used in said step (i) is elemental sulphur.

10. Use of a thermoplastic copolymer with a high sulphur content according to claim 1, as is or mixed with other (co)polymers, such as styrene, divinylbenzene, in packages, electronics, household appliances, computer cases, CD cases, kitchen, laboratory, office and medical items, building and construction industries.

Description

DETAILED DESCRIPTION

[0029] Therefore, further subject matter of the present patent application is a process for the preparation of a thermoplastic copolymer with a high sulphur content comprising: [0030] (i) reacting the sulphur with at least one monomer having general formula (I), in the presence of at least one radical initiator and at least one radical chain terminator, at a temperature comprised between 120° C. and 190° C., preferably comprised between 130° C. and 180° C., for a time comprised between 1 minute and 180 minutes, preferably comprised between 10 minutes and 130 minutes, thus obtaining a liquid pre-polymer; [0031] (ii) pouring the liquid pre-polymer obtained in step (i) into a mould and keep said mould at a temperature comprised between 100° C. and 180° C., preferably comprised between 120° C. and 170° C., for a time comprised between 1 hour and 24 hours, preferably comprised between 2 hours and 18 hours, thus obtaining a thermoplastic copolymer with a high sulphur content.

[0032] According to a preferred embodiment of the present disclosure, said radical initiator is selected from: mercaptans such as, for example, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercapto-benzimidazole, 2,5-dimercapto-1,3,4-thiadiazole, 2-mercapto-2,5-dimethylaminopyridine, or mixtures thereof alkenyl disulphides such as, for example, diallyl disulphide, allyl propyl disulphide, ethyl allyl disulphide, methyl allyl disulphide, or mixtures thereof; or mixtures thereof. Mercaptobenzothiazole, diallyl disulphide are preferred.

[0033] According to a preferred embodiment of the present disclosure, said radical initiator can be used in said step (i) in an amount less than or equal to 1% by weight, preferably comprised between 0.2% by weight and 0.5% by weight, in relation to the total weight of the reaction mixture (i.e. the mixture of sulphur+monomer+radical initiator+radical chain terminator).

[0034] According to a preferred embodiment of the present disclosure, said radical chain terminator can be selected, for example, from aliphatic, cycloaliphatic or aromatic disulphides, such as, for example, dimethyl disulphide, diethyl disulphide, dicyclohexyl disulphide, diphenyl disulphide, ditolyl disulphide, or derivatives thereof, or mixtures thereof. Diethyl disulphide, dicyclohexyl disulphide, diphenyl disulphide, are preferred.

[0035] According to a preferred embodiment of the present disclosure, said radical chain terminator can be used in said step (i) in an amount less than or equal to 15% by weight, preferably comprised between 5% by weight and 10% by weight, in relation to the total weight of the reaction mixture (i.e. the mixture of sulphur+monomer+radical initiator+radical chain terminator).

[0036] For the purpose of the process according to the present disclosure, the mould used in the aforesaid step (iii) can preferably be made of teflon or silicone.

[0037] According to a preferred embodiment of the present disclosure the sulphur used in said step (i) is elemental sulphur.

[0038] For the purpose of the process according to the present disclosure, said elemental sulphur is preferably in the form of powder or “flakes”. In environmental conditions (i.e. at ambient temperature and pressure), the elemental sulphur exists in orthorhombic crystalline form (ring with eight sides) (S.sub.8) and has a melting point comprised between 120° C. and 124° C. Said elemental sulphur in orthorhombic crystalline form (S.sub.8), at a temperature greater than 159° C., is subject to “Ring Opening Polymerization” (ROP) and is transformed into a linear polymer chain with two free radicals at the ends. Said linear polymer chain is metastable and therefore it tends to be reconverted to the orthorhombic crystalline form (S.sub.8) at different speeds according to the conditions.

[0039] For the purpose of the process according to the present disclosure, said elemental sulphur is in the orthorhombic crystalline form (S.sub.8) said form generally being the most stable, the most accessible and the least expensive. However, it is to be noted that, for the purpose of the present disclosure, other allotropic forms of sulphur can be used such as, for example, the cyclic allotropic forms deriving from thermal processes to which the elemental sulphur in orthorhombic crystalline form (S.sub.8) can be subjected. It is also to be noted that any species of sulphur that, when heated, enables species able to be subjected to radical or anionic polymerization to be obtained, can be used for the purpose of the process according to the present disclosure.

[0040] As mentioned above, said thermoplastic copolymer with a high sulphur content can be advantageously used, as such, or mixed with other (co)polymers (for example, styrene, divinylbenzene), in different applications such as, for example, packaging, electronics, household appliances, computer cases, CD cases, kitchen, laboratory, office and medical items, building and construction industries.

[0041] Therefore, further subject matter of the present disclosure is the use of said thermoplastic copolymer with a high sulphur content, as such, or mixed with other (co)polymers (for example, styrene, divinylbenzene), in different applications such as, for example, packaging, electronics, household appliances, computer cases, CD cases, kitchen, laboratory, office and medical items, building and construction industries.

[0042] In order to better understand the present disclosure and to put it into practice, some illustrative and non-limiting examples thereof are reported below.

EXAMPLES

Analysis and Characterization Methodologies

[0043] The analysis and characterization methodologies reported below were used.

DMA—“Dynamic Mechanical Analysis”

[0044] The DMA—“Dynamic Mechanical Analysis” was performed using an RMS 800 rheometer by Rheometrics Scientific, equipped with 25 mm parallel plates geometry.

[0045] For that purpose, after conditioning the sample of copolymer obtained in a drier containing silica gel, for one night, a disc shaped sample with a diameter of 25 mm and thickness of 2 mm was obtained, by hot moulding, operating as described below.

[0046] The disc shaped sample thus obtained was inserted between the parallel plates of the aforesaid rheometer and the complex viscosity (η*) was measured, at a constant temperature equal to 160° C., applying strain of 10%, as the oscillation frequency of the plates varies from 0.01 rad/s to 100 rad/s.

Differential Scanning Calorimetry (DSC)

[0047] Differential Scanning calorimetry, for the purpose of determining the glass transition temperature (T.sub.g) of the copolymers obtained, was performed using a Perkin Elmer Pyris differential scanning calorimeter, using the following thermal program: [0048] cooling from ambient temperature (T=25° C.) to −60° C. at a speed of −5° C./minute; [0049] heating from −60° C. to +150° C. at a speed of +10° C./minute (first scan); [0050] cooling from +150° C. to −60° C. at a speed of −5° C./minute; [0051] heating from −60° C. to +150° C. at a speed of +10° C./minute (second scan); operating under nitrogen (N.sub.2) flow at 70 ml/minute.

Hot Moulding

[0052] For that purpose, 5 g of the copolymer obtained were placed between two teflon sheets, in turn positioned between two metal sheets having the following dimensions: 25 cm×25 cm, 1 mm thick. Everything was inserted into a hot press previously brought to the final pressing temperature (160° C.) and the hot plates were moved towards one another until obtaining good contact with the metal sheets. When the softening of the copolymer was observed, after about 10 minutes, pressing began with a load of less than 1.5 tonnes. After obtaining sufficient lowering of the applied load (due to the deformation of the copolymer) the applied load was brought to a value greater than 1 tonne and less than 1.5 tonnes: said operation was repeated 2 or 3 times until obtaining a disc shaped product.

Example 1 (Comparative)

[0053] Synthesis of Copolymer with Sulphur (60% by weight) and Dicyclopentadiene (40% by weight)

[0054] 60 g of pure sulphur were loaded cold [elemental sulphur in crystalline orthorhombic form (S.sub.8) by Sigma-Aldrich] into a 250 jacketed reactor: the reactor was heated to 140° C., through a thermostat with silicone oil circulation as working fluid. Then, through a jacketed dropping funnel, the following were added in this order: 40 g of dicyclopentadiene (purity >96%−Sigma-Aldrich) previously liquefied and 0.4 ml of diallyl disulphide (Sigma-Aldrich): everything was kept, in an inert atmosphere, under mechanical agitation through a compressed air explosion-proof agitator drill, at 140° C., for 90 minutes, obtaining a pre-polymerized fluid. The pre-polymerized fluid thus obtained was poured into a teflon mould which was closed and placed in a pre-heated oven at 140° C.: said pre-polymerized fluid was kept at said temperature, for 16 hours, obtaining a rigid, very resistant and difficult to break, black copolymer.

[0055] Said copolymer was subjected to DMA (“Dynamic Mechanical Analysis”) operating as described above, for the purpose of measuring the complex dynamic viscosity (η*). It was not possible to determine the complex dynamic viscosity (η*) as the sample crumbled.

[0056] Said copolymer was also subjected to DSC (“Differential Scanning calorimetry”) operating as described above, for the purpose of measuring the glass transition temperature (T.sub.g) which was equal to 93° C.

[0057] Furthermore, said copolymer, when subjected to hot moulding operating as described above, could not be moulded as it crumbled.

Example 2 (Disclosure)

[0058] Synthesis of Copolymer with Sulphur (60% by weight), Dicyclopentadiene (35% by weight) and Diethyl Disulphide (5% by weight)

[0059] 60 g of pure sulphur were loaded cold [elemental sulphur in crystalline orthorhombic form (S.sub.8) by Sigma-Aldrich] and 0.4 g of 2-mercaptobenzodiazole (Aldrich) into a 250 jacketed reactor: the reactor was heated to 140° C., through a thermostat with silicone oil circulation as working fluid. Then, through a jacketed dropping funnel, the following were added in this order: 35 g of dicyclopentadiene (purity>96%—Sigma-Aldrich) previously liquefied and 5 ml of diethyl disulphide (Sigma-Aldrich): everything was kept, in an inert atmosphere, under mechanical agitation through a compressed air explosion-proof agitator drill, at 160° C., for 120 minutes, obtaining a pre-polymerized fluid. The pre-polymerized fluid thus obtained was poured into a teflon mould which was closed and placed in a pre-heated oven at 160° C.: said pre-polymerized fluid was kept at said temperature, for 16 hours, obtaining a rigid, very resistant and difficult to break, black copolymer.

[0060] Said copolymer was subjected to DMA—“Dynamic Mechanical Analysis” operating as described above, for the purpose of measuring the complex dynamic viscosity (η*) which was equal to 7×10.sup.5 Pa.s.

[0061] Said copolymer was also subjected to DSC (“Differential Scanning calorimetry”) operating as described above, for the purpose of measuring the glass transition temperature (T.sub.g) which was equal to 88° C.

[0062] Furthermore, said copolymer, when subjected to hot moulding operating as described above, could be moulded as it appeared deformed but uniform, cohesive, in a single body and with a relaxed surface.

Example 3 (Disclosure)

[0063] Synthesis of Copolymer with Sulphur (60% by weight), Dicyclopentadiene (35% by weight) and Dicyclohexyl Disulphide (5% by weight)

[0064] 60 g of pure sulphur were loaded cold [elemental sulphur in crystalline orthorhombic form (S.sub.8) by Sigma-Aldrich] and 0.4 g of 2-mercaptobenzodiazole (Aldrich) into a 250 jacketed reactor: the reactor was heated to 140° C., through a thermostat with silicone oil circulation as working fluid. Then, through a jacketed dropping funnel, the following were added in this order: 35 g of dicyclopentadiene (purity>96%—Sigma-Aldrich) previously liquefied and 4.8 ml of dicyclohexyl disulphide (Sigma-Aldrich): everything was kept, in an inert atmosphere, under mechanical agitation through a compressed air explosion-proof agitator drill, at 160° C., for 120 minutes, obtaining a pre-polymerized fluid. The pre-polymerized fluid thus obtained was poured into a teflon mould which was closed and placed in a pre-heated oven at 160° C.: said pre-polymerized fluid was kept at said temperature, for 16 hours, obtaining a rigid, very resistant and difficult to break, black copolymer.

[0065] Said copolymer was subjected to DMA—“Dynamic Mechanical Analysis” operating as described above, for the purpose of measuring the complex dynamic viscosity (η*) which was equal to 6×10.sup.5 Pa.s.

[0066] Said copolymer was subjected to DSC (“Differential Scanning calorimetry”) operating as described above, for the purpose of measuring the glass transition temperature (T.sub.g) which was equal to 98° C. Said copolymer was very resistant and difficult to break.

[0067] Furthermore, said copolymer, when subjected to hot moulding operating as described above, could be moulded as it appeared deformed but uniform, cohesive, in a single body and with a relaxed surface.