Process for producing a multilayer laminate

1. A process for producing a multilayer laminate being a photovoltaic (PV) module comprising, in the given order, a protective front layer element, a front encapsulation layer element, a photovoltaic element, a rear encapsulation layer element, and a protective back layer element,

wherein any one or more of the front encapsulation layer element or rear encapsulation layer element is/are a polymeric layer element(s) (LE);

the protective front layer element is a first substrate element being a glass element; and

the protective back layer element is a second substrate element being a glass element;

wherein the polymeric layer element (LE) comprises a polymer composition comprising:

(a) a polymer;

and wherein the process comprises the steps of:

(i) assembling step to arrange the at least one substrate element and the at least one polymeric layer element (LE) in form of a multilayer assembly;

(ii) heating step to heat up the multilayer assembly;

(iii) pressure build up step, where the pressure on the multilayer assembly is gradually increased in a single or multiple steps;

(iv) pressure holding step, where the pressure is kept on the multilayer assembly at the heated conditions attained at the end of step (ii); and

(v) recovering step to cool and remove the obtained multilayer laminate for later use;

wherein the pressure during pressure holding step (iv) is kept at 790 mbar or below; and

wherein average thickness variation of the resultant multilayer laminate is 60% or less, wherein the average thickness variation (%) is the average of the thickness variation of two opposite edges of the multilayer laminate compared to the middle of the multilayer laminate.

2. The process according to claim 1 , wherein the pressure holding step (iv) is kept at pressure of 700 mbar or less.

3. The process according to claim 1 , wherein the duration of the pressure holding step (iv) is 0.5 to 20 minutes.

4. The process according to claim 1 , wherein the pressure build up step (iii) is started when the at least one polymeric layer element (LE) reaches a temperature which is at least 3 to 10° C. higher than the melting temperature of the polymer (a) of said polymeric layer element (LE).

5. The process according to claim 1 , wherein said polymer (a) is a polymer of ethylene; and

(b) silane group(s) containing units.

6. The process according to claim 1 , wherein the polymer composition of the polymeric layer of the lamination process comprises:

a polymer of ethylene (a) selected from:

(a1) a polymer of ethylene which bears functional groups containing units;

(a2) a polymer of ethylene containing one or more polar comonomer(s) selected from (C1-C6)-alkyl acrylate or (C1-C6)-alkyl (C1-C6)-alkylacrylate; or

(a3) a polymer of ethylene containing one or more alpha-olefin comonomer selected from (C1-C10)-alpha-olefin comonomer; and

silane group(s) containing units (b).

7. The process according to claim 1 , wherein the polymer composition comprises:

polymer (a) which is selected from:

(a1) a polymer of ethylene; or

(a2) a polymer of ethylene containing one or more polar comonomer(s) selected from (C1-C6)-alkyl acrylate or (C1-C6)-alkyl (C1-C6)-alkylacrylate comonomer(s); and

silane group(s) containing units (b).

8. The process according to claim 1 , wherein the polymer composition comprises:

polymer (a) which is selected from

(a1) a polymer of ethylene; or

(a2) a polymer of ethylene containing one or more polar comonomer(s) selected from (C1-C6)-alkyl acrylate or (C1-C6)-alkyl (C1-C6)-alkylacrylate comonomer(s); and

silane group(s) containing units (b); or

wherein the polymer composition comprises:

a polymer (a) which is the polymer of ethylene (a1) which bears the silane group(s) containing units (b) as the functional groups containing units, or

the polymer composition comprises:

a polymer (a) which is the polymer of ethylene (a2) containing one or more polar comonomer(s) selected from (C1-C6)-alkyl acrylate or (C1-C6)-alkyl (C1-C6)-alkylacrylate, and bears functional group(s) containing units other than said polar comonomer; and

silane group(s) containing units (b).

9. The process according to claim 5 , wherein the silane group(s) containing unit (b) is a hydrolysable unsaturated silane compound represented by the formula (I):

R1SiR2 q Y 3−q   (I)

wherein

R1 is an ethylenically unsaturated hydrocarbyl, hydrocarbyloxy or (meth)acryloxy hydrocarbyl group,

each R2 is independently an aliphatic saturated hydrocarbyl group,

Y which may be the same or different, is a hydrolysable organic group and

q is 0, 1 or 2, the amount of the silane group(s) containing units (b) present in the layer is from 0.01 to 1.00 mol %, when determined via quantitative 1 H NMR spectroscopy.

10. The process according to claim 1 , wherein polymer (a) is a copolymer of ethylene (a1) with vinyl trimethoxysilane comonomer or a copolymer of ethylene (a2) with methylacrylate comonomer and with vinyl trimethoxysilane comonomer.

11. The process according to claim 1 , wherein no peroxide crosslinking agent is introduced to the polymer (a) of the polymer composition before or during the lamination process.

12. The process according to claim 1 , wherein the copolymer of ethylene (a) has one, more or all of the following properties

melt flow rate, MFR 2 , of less than 20 g/10 min (according to ISO 1133 at 190° C. and at a load of 2.16 kg),

Melting temperature, Tm, of 100° C. or less when measured according to ISO 3146, and/or

Shear thinning index, SHI 0.05/300 , of 30.0 to 100.0 when determined by Dynamic Shear Measurements (frequency sweep measurements).

13. A photovoltaic (PV) module obtainable by the process according to claim 1 .

14. The process according to claim 5 , wherein the polymer composition of the polymeric layer of the lamination process comprises:

a polymer of ethylene (a) selected from:

(a1) a polymer of ethylene which contains one or more comonomer(s) other than a polar comonomer of polymer (a2) and which bears functional groups containing units;

(a2) a polymer of ethylene containing one or more polar comonomer(s) selected from (C1-C6)-alkyl acrylate or (C1-C6)-alkyl (C1-C6)-alkylacrylate, and bears functional group(s) containing units other than said polar comonomer; or

(a3) a polymer of ethylene containing one or more alpha-olefin comonomer selected from (C1-C10)-alpha-olefin comonomer; and bears functional group(s) containing units; and

silane group(s) containing units (b).

15. The process according to claim 1 , wherein no crosslinking agent selected from peroxide or silane condensation catalyst (SCC), which is selected from the SCC group of carboxylates of tin, zinc, iron, lead or cobalt or aromatic organic sulphonic acids, is introduced to the polymer (a) of the polymer composition before or during the lamination process.

16. The process according to claim 1 , wherein the pressure holding step (iv) is kept at pressure of 0 to 440 mbar.