Masterbatch and process for preparing a polymer composition

1. A process for producing a polymer composition comprising the steps of

a) providing a masterbatch (MB) which comprises at least one water tree retardant (WTR) additive and a carrier polymer, and

b) blending the masterbatch obtained from step a) with at least one LDPE polymer (A) produced in a high pressure process, to obtain said polymer composition;

wherein the carrier polymer and the LDPE polymer (A) are different, and

wherein the masterbatch (MB) comprises:

one or more WTR additive(s), wherein the total amount of the one or more WTR additive(s) is of less than 50 wt %, based on the total amount (wt %) of the MB and

a carrier polymer in an amount of at least 50 wt % based on the total amount of the MB wherein the carrier polymer is a polar polyethylene.

2. The process according to claim 1 wherein step a) comprises providing a MB having one or more WTR additive(s), wherein the total amount of one or more WTR additive(s) is of more than 0.5 wt % based on the total amount of the MB, and a carrier polymer in an amount of at least 50 wt % based on the total amount of the MB.

3. The process according to claim 1 wherein step b) comprises blending up to 20 wt % of the MB of step a), based on the total amount of the polymer composition, to the LDPE (A).

4. The process according to claim 1 , wherein:

step a) comprises providing the MB by incorporating the one or more WTR additive(s) to the carrier polymer by meltmixing the one or more WTR additive(s) with the carrier polymer at an elevated temperature above the melting or softening temperature of at least the carrier polymer, and

step b) comprises blending the obtained MB of step (a) with the LDPE (A).

5. The process according to claim 1 , wherein the one or more WTR additive(s) comprise at least one ether and/or ester group containing compound selected from the group comprising:

1) a polyethylene glycol(s),

2) a glycerol ester compound(s),

3) a polypropylene glycol(s),

4) an amido group containing fatty acid ester(s),

5) an ethoxylated and/or propoxylated pentaerythritol(s),

6) an alpha-tocopherol ester(s),

7) an ethoxylated and/or propoxylated fatty acid(s), including any derivatives of the compounds of groups 1)-7), or from any mixture(s) of WTR additive(s) of the group(s) of 1)-7).

6. The process according to claim 1 , wherein the MB contains one or more WTR additive(s) selected from the group consisting of:

1) polyethylene glycol(s),

2) glycerol ester(s) and

a combination of 1) polyethylene glycol(s) and 2) glycerol ester(s).

7. The process according to claim 5 , wherein 1) the polyethylene glycol(s), if present, have a formula HO(CH 2 CH 2 O) x H, and wherein 2) the glycerol ester(s), if present, are obtained by esterification of glycerol or a polyglycerol with at least one carboxylic acid.

8. The process according to claim 1 , wherein:

a) the MB of step a)

comprises

one or more WTR additive(s), wherein the total amount of the one or more WTR additive(s) is of less than 50 wt % based on the total amount (wt %) of the MB, and wherein at least one WTR additive(s) is an organic compound containing at least one ether and/or ester group, and

a carrier polymer in an amount of at least 50 wt % based on the total amount of the MB B), and wherein the carrier polymer is a polar polyethylene.

9. The process according to claim 8 , wherein

the polar polyethylene contains a polar comonomer(s) which contains hydroxyl group(s), alkoxy group(s), carbonyl group(s), carboxyl group(s), ether group(s) or ester group(s), or any mixture thereof.

10. A process for producing a cable comprising a conductor surrounded by one or more layers, wherein the process comprises:

(I) producing a polymer composition according to the process of claim 1 ;

and

(II) applying the polymer composition of step (I) on the conductor for forming at least one layer of said at least one or more layers.

11. The process of claim 10 for producing a cable, wherein:

step (I) comprises:

a) providing the MB in the form of pellets,

b) blending the pellets of MB obtained from step a), optionally together with further component(s), to the LDPE (A) by meltmixing to obtain said polymer composition, and

step (II) comprises applying the obtained melt mixture of the polymer composition of step b) on the conductor to form the at least one layer.

12. The process of claim 10 , wherein the cable produced is a power cable, comprising at least an inner semiconductive layer, an insulation layer and an outer semiconductive layer in the given order, and wherein the at least one layer formed in step (II) is the insulation layer.

13. The process according to claim 4 , further comprising pelletizing the MB obtained in step (a).

14. The process according to claim 10 , further comprising crosslinking the layer formed in step (II) in the presence of a crosslinking agent.

15. The process according to claim 11 , further comprising crosslinking the layer formed in step (II) in the presence of a crosslinking agent.

16. The process according to claim 12 , further comprising crosslinking the layer formed in step (II) in the presence of a crosslinking agent.