Multilayer transparent polyester film, method for manufacturing said film and use of said film in particular in the backsheets of photovoltaic panels

• US 10,714,641 B2
• Filed: 01/30/2015
• Issued: 07/14/2020
• Est. Priority Date: 01/31/2014
• Status: Active Grant

• Current Assignee: Toray Films Europe (Toray Industries Incorporated)
• Original Assignee: Toray Films Europe (Toray Industries Incorporated)
• Inventors: Lacrampe, Valerie
• Primary Examiner(s): Chen, Vivian
• Application Number:
  US15/115,373
• Publication Number:
  US 20170012151A1
• Time in Patent Office: 1,992 Days
• Field of Search: None
• CPC Class Codes: B29C 48/16 Articles comprising two or more components, e.g. co-extruded layers
• CPC Class Codes: B29C 48/18 the components being layers
• CPC Class Codes: B29D 7/01 Films or sheets
• CPC Class Codes: B29K 2067/00 Use of polyesters or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2067/003 PET, i.e. poylethylene terephthalate
• CPC Class Codes: B32B 2038/0028 Stretching, elongating
• CPC Class Codes: B32B 2038/0048 Annealing, relaxing
• CPC Class Codes: B32B 2250/02 2 layers
• CPC Class Codes: B32B 2250/03 3 layers
• CPC Class Codes: B32B 2250/244 All polymers belonging to those covered by group B32B27/36
• CPC Class Codes: B32B 2250/40 Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA
• CPC Class Codes: B32B 2264/00 Composition or properties of particles which form a particulate layer or are present as additives
• CPC Class Codes: B32B 2264/102 Oxide or hydroxide
• CPC Class Codes: B32B 2264/104 Oxysalt, e.g. carbonate, sulfate, phosphate or nitrate particles
• CPC Class Codes: B32B 2270/00 Resin or rubber layer containing a blend of at least two different polymers
• CPC Class Codes: B32B 2307/40 having particular optical properties light or UV resistant B32B2307/71
• CPC Class Codes: B32B 2307/412 Transparent
• CPC Class Codes: B32B 2307/518 bi-axially
• CPC Class Codes: B32B 2307/71 Resistive to light or to UV
• CPC Class Codes: B32B 2307/746 Slipping, anti-blocking, low friction
• CPC Class Codes: B32B 2367/00 : Polyesters, e.g. PET, i.e. polyethylene terephthalate
• CPC Class Codes: B32B 2457/12 : Photovoltaic modules
• CPC Class Codes: B32B 27/08 : of synthetic resin
• CPC Class Codes: B32B 27/18 : characterised by the use of special additives
• CPC Class Codes: B32B 27/20 : using fillers, pigments, thixotroping agents
• CPC Class Codes: B32B 27/36 : comprising polyesters
• CPC Class Codes: B32B 37/15 : with at least one layer being manufactured and immediately laminated before reaching its stable state, e.g. in which a layer is extruded and laminated while in semi-molten state
• CPC Class Codes: B32B 37/153 : at least one layer is extruded and immediately laminated while in semi-molten state
• CPC Class Codes: C08K 2003/321 : Phosphates
• CPC Class Codes: C08K 2003/324 : Alkali metal phosphate
• CPC Class Codes: C08K 2003/329 : Phosphorus containing acids
• CPC Class Codes: C08K 3/013 : Fillers, pigments or reinforcing additives
• CPC Class Codes: C08K 3/014 : Stabilisers against oxidation, heat, light or ozone
• CPC Class Codes: C08K 3/32 : Phosphorus-containing compounds
• CPC Class Codes: C08K 5/005 : Stabilisers against oxidation, heat, light, ozone
• CPC Class Codes: C08K 5/09 : Carboxylic acids; Metal salts thereof; Anhydrides thereof
• CPC Class Codes: C08K 5/098 : Metal salts of carboxylic acids
• CPC Class Codes: C08K 5/52 : Phosphorus bound to oxygen only
• CPC Class Codes: C08K 5/521 : Esters of phosphoric acids, e.g. of H3PO4
• CPC Class Codes: C08L 2201/08 : Stabilised against heat, light or radiation or oxydation
• CPC Class Codes: C08L 2201/10 : Transparent films; Clear coatings; Transparent materials
• CPC Class Codes: C08L 2203/16 : used for films
• CPC Class Codes: C08L 2203/204 : use in solar cells
• CPC Class Codes: C08L 2205/02 : containing two or more polymers of the same C08L -group
• CPC Class Codes: C08L 67/02 : Polyesters derived from dicarboxylic acids and dihydroxy compounds C08L67/06 takes precedence
• CPC Class Codes: C08L 67/03 : the dicarboxylic acids and dihydroxy compounds having the carboxyl- and the hydroxy groups directly linked to aromatic rings
• CPC Class Codes: H01L 31/049 : Protective back sheets
• CPC Class Codes: Y02E 10/50 : Photovoltaic [PV] energy
• CPC Class Codes: Y10T 428/24355 : Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/24413 : Metal or metal compound
• CPC Class Codes: Y10T 428/25 : Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/258 : Alkali metal or alkaline earth metal or compound thereof
• CPC Class Codes: Y10T 428/31786 : Of polyester [e.g., alkyd, etc.]

Abstract

A biaxially oriented multilayer transparent film including at least two layers of polyester, respectively a core layer and at least one outer layer, which can be identical or different, wherein: i) at least the core layer includes at least one biaxially oriented transparent polyester PE1, ii) at least one of the outer layers includes, on the one hand, at least one biaxially oriented polyester PE2, and, on the other hand, particles coming from the reaction between at least one metal compound and at least one monomeric or oligomeric unit of PE2, the particles having more preferably a d50—as μm and following an order of preference—between 0.5 and 5; between 1.0 and 4, and between 1.5 and 3.0. Also relates to the manufacture of this film and its applications as a laminate in particular in the backsheets of photovoltaic cells.

Claims

1. Transparent multilayered film, biaxially stretched, comprising at least 2 layers of polyester including a core layer and at least one outer layer, wherein:

i) at least the core layer contains at least a transparent biaxially oriented polyester PE1 that is a polyester PEα

;

comprising an alkali metal phosphate in a concentration of 1.3 mole/ton to 3.0 mole/ton, and phosphoric acid in a concentration of 0.4 to 1.5 times (per mole) the concentration of the alkali metal phosphate, and

in which an increase of COOH in PE1 between before and after a wet-heating treatment performed at 155°

C. for 4 hours under saturated steam is 90 eq./ton or less,

ii) the at least one outer layer comprises at least a biaxially oriented polyester PE2, and particles formed during formation of PE2 by reaction between at least one metallic compound and at least a monomer or oligomer unit of a precursor PE2″

of PE2, wherein the metallic compound that is able to react with the at least one monomer or oligomer unit of the precursor PE2″

, in order to form the particles, is selected from a group consisting of metallic salts of carboxylic acids, organophosphates derived from phosphoric acid, and blends thereof,

the particles have a d50 in μ

m of from 1.5 to 3, and

the PE2 is obtained by solid state post-condensation from the precursor PET′

;

iii) at least one of the at least one outer layers comprises at least the PE2 and at least the PE1; and

iv) at least one of the core layer and the at least one outer layer(s) includes a photo stabilizer.

2. A film according to claim 1, wherein the film comprises the core layer and at least one of the outer layers on each of opposite sides of the core layer.

3. A method of manufacturing a multilayer biaxially oriented polyester film according to claim 1, the manufacturing method comprising:

(i) synthesis or implementation of at least one of the PE1 and at least one of the PE2;

(ii) optional pre-drying of the polyesters;

(iii) heating the polyesters to form molten polyesters that are malleable;

(iv) extruding the molten polyesters to form the multilayer film;

(v) quenching and solidifying the multilayer film;

(vi) bi-axial stretching the multilayer film in longitudinal and transverse directions of the multilayer film, at a given stretching temperature Ts; and

(vii) heating the biaxially stretched film at a given heating temperature Th.

4. A laminate comprising the film according to claim 1.

5. Transparent photovoltaic panel, whose rear surface (backsheet) comprises the film according to claim 1.

6. A film according to claim 1, wherein a proportion of PE2 and the particles in the at least one of the outer layers, and a total thickness of the outer layer(s) comprising PE2 and the particles, are such that:

the haze of the film is less than or equal to 2.5; and

the Kd (dynamic friction coefficient) of the film is less or equal to 0.5.

7. A film according to claim 1, wherein a proportion of PE2 and the particles in the at least one of the outer layers, and a total thickness of the outer layer(s) comprising PE2 and the particles, are such that:

a haze of the film is less than or equal to 3.0; and

Kd (dynamic friction coefficient) of the film is less or equal to 0.65.