KR20230007825A - Flame-retardant Polypropylene Resin Composition with Excellent Transparency - Google Patents

Abstract

The present invention relates to a polypropylene resin composition containing a non-halogen flame retardant and having excellent flame retardancy and flame proofness, and molded articles manufactured therefrom. The polypropylene resin composition according to an embodiment of the present invention is excellent in both transparency and flame retardancy, and thus, can be effectively used for films, sheets and the like requiring transparency and flame retardancy.

Description

Flame retardant polypropylene resin composition with excellent transparency {Flame-retardant Polypropylene Resin Composition with Excellent Transparency}

The present invention relates to a flame retardant polypropylene resin composition having excellent transparency and a molded article prepared therefrom. Specifically, the present invention relates to a polypropylene resin composition containing a non-halogen flame retardant and having excellent flame retardancy and flame retardancy as well as transparency, and a molded article manufactured therefrom.

Polypropylene resin, a type of general-purpose resin, has excellent mechanical properties, formability, and chemical resistance as well as economic feasibility. It is used in various ways.

Since these polypropylene resins are basically inflammable materials, attempts have been made to impart flame retardancy to polypropylene resins. In particular, in preparation for the case where the polypropylene resin is in direct contact with a flame, studies have been mainly conducted to increase flame retardancy.

For example, Korean Patent Application Publication No. 1997-0074843 attempted to secure flame retardancy of a polypropylene resin by using a brominated compound flame retardant and an inorganic flame retardant, antimony oxide, in combination. In this case, the flame retardancy of the polypropylene resin is improved, but there is a problem of corrosion of metal surfaces such as molds due to generation of harmful gases during combustion or processing at high temperatures. In addition, antimony oxide flame retardant reduces the transparency of polypropylene resin, and its application is limited to fields requiring high transparency.

In addition, Korean Patent No. 2107912 discloses a polypropylene resin composition comprising a mixture of a halogen-based flame retardant and a phosphorus-based flame retardant and a nucleating agent. Although this composition exhibits excellent flame retardancy and transparency, halogen-based flame retardants are still used, and its use is limited to injection molding.

Therefore, development of a polypropylene resin composition excellent in both flame retardancy and transparency has been required.

Korean Patent Application Publication No. 1997-0074843 Korean Patent No. 2107912

Accordingly, an object of the present invention is to provide a polypropylene resin composition excellent in both transparency and flame retardancy and a molded article produced therefrom.

According to one embodiment of the present invention for achieving the above object, based on the total weight of components (A) and (B), (A) from propylene homopolymer, propylene-α-olefin random copolymer and mixtures thereof 95.0 to 99.0% by weight of a selected polypropylene resin; and (B) 0.5 to 5% by weight of a non-halogen flame retardant, wherein the non-halogen flame retardant is cyclohexane and peroxidized N-butyl-2,2,6,6-tetramethyl-4-piperidinamine 1,3-propanediamine combined with -2,4,6-trichloro-1,3,5-triazine reaction product, N,N-1,2-ethanediylbis-, flame retardant polypropylene as a reaction product A resin composition is provided.

In a preferred embodiment of the present invention, the polypropylene-based resin (A) may further include an ethylene-propylene block copolymer in an amount of 20% by weight or less based on the total weight of the polypropylene-based resin.

In a preferred embodiment of the present invention, the melt index of the polypropylene-based resin (A) may be 0.1 to 50 g/10 minutes when measured at 230° C. under a load of 2.16 kg based on ASTM D1238.

In a preferred embodiment of the present invention, the flame retardant polypropylene resin composition is transparent, based on 100 parts by weight of components (A) and (B), (C) a sorbitol-based nucleating agent, a nonitol-based nucleating agent, and a mixture thereof selected from the group consisting of A nucleating agent may be further included in an amount of 500 to 10,000 ppm.

In a preferred embodiment of the present invention, the sorbitol-based nucleating agent is benzylidenesorbitol, bisbenzylidenesorbitol, methylbenzylidenesorbitol, bismethylbenzylidenesorbitol, ethylenebenzylidenesorbitol, bisethylbenzylidenesorbitol, 3,4-dimethylbenzylidene consisting of sorbitol, 2-chloro-2,4-methylbenzylidenesorbitol, 1,3-chloro-2,4-methylbenzyl sorbitol and 1,3,2,4-bis-3,4-dimethylbenzylidenesorbitol It may be at least one selected from the group.

In a preferred embodiment of the present invention, the nonitol-based nucleating agent may be 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol.

In a preferred embodiment of the present invention, the flame retardant polypropylene resin composition may further include an additive (D) in an amount of 2 parts by weight or less based on 100 parts by weight of components (A) and (B). In this case, the additive (D) may be at least one selected from the group consisting of an antioxidant, a neutralizer, a reinforcing agent, a filler, a weathering stabilizer, an antistatic agent, a lubricant, a slip agent, a pigment, and a dye.

In a preferred embodiment of the present invention, additive (D) is pentaerythritol tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate), 1,3,5-trimethyl- at least one antioxidant selected from the group consisting of tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene and tris(2,4-di-t-butylphenyl)phosphite. .

In a preferred embodiment of the present invention, additive (D) may be at least one neutralizing agent selected from the group consisting of hydrotalcite and calcium stearate.

According to another embodiment of the present invention, a flame retardant polypropylene resin molded article prepared by molding the above polypropylene resin composition is provided.

In a preferred embodiment of the present invention, the flame retardant polypropylene resin molded article may be a film or sheet.

In a preferred embodiment of the present invention, the flame retardant polypropylene resin molded article may exhibit flame retardancy of UL-94 VTM-0 or higher and haze of 10% or less based on a thickness of 40 to 150 μm.

The polypropylene resin composition according to an embodiment of the present invention is excellent in both transparency and flame retardancy, and can be effectively used for films and sheets requiring transparency and flame retardancy.

Hereinafter, the present invention will be described in more detail.

According to one embodiment of the present invention, based on the total weight of components (A) and (B), (A) a polypropylene-based resin selected from propylene homopolymers, propylene-α-olefin random copolymers and mixtures thereof 95.0 -99.0% by weight; and (B) 0.5 to 5% by weight of a non-halogen flame retardant, wherein the non-halogen flame retardant is cyclohexane and peroxidized N-butyl-2,2,6,6-tetramethyl-4-piperidinamine 1,3-propanediamine combined with -2,4,6-trichloro-1,3,5-triazine reaction product, N,N-1,2-ethanediylbis-, flame retardant polypropylene as a reaction product A resin composition is provided.

(A) polypropylene resin

The flame retardant polypropylene resin composition according to an embodiment of the present invention includes a polypropylene-based resin (A) selected from propylene homopolymers, propylene-α-olefin random copolymers, and mixtures thereof.

Here, the propylene homopolymer may be a polymer obtained by polymerizing a propylene monomer substantially alone.

There is no particular limitation on the method for preparing the propylene homopolymer, and a method for preparing the propylene homopolymer known in the art may be used as it is or modified appropriately. For example, a bulk polymerization method, a solution polymerization method, a slurry polymerization method, a gas phase polymerization method, or the like can be used, and either a batch polymerization method or a continuous polymerization method is possible.

The propylene-α-olefin random copolymer may be a random copolymer of propylene and ethylene or propylene and an α-olefin having 4 or 8 carbon atoms. In addition, the propylene-α-olefin random copolymer may be a tertiary random copolymer of propylene, ethylene, and an α-olefin having 4 or 8 carbon atoms.

There is no particular limitation on the method for preparing the propylene-α-olefin random copolymer, and a method for preparing a propylene homopolymer known in the art to which the present invention pertains may be used as it is or modified appropriately. For example, a bulk polymerization method, a solution polymerization method, a slurry polymerization method, a gas phase polymerization method, or the like can be used, and either a batch polymerization method or a continuous polymerization method is possible.

In a preferred embodiment of the present invention, the polypropylene-based resin (A) may further include an ethylene-propylene block copolymer in an amount of 20% by weight or less based on the total weight of the polypropylene-based resin. When the polypropylene-based resin (A) further includes an ethylene-propylene block copolymer, mechanical properties such as tensile strength and flexural modulus are improved, but when the content exceeds 20% by weight, molded articles, particularly films or sheets, are deteriorated. Transparency may be reduced.

Here, the ethylene-propylene block copolymer may be obtained by stepwise polymerization of a propylene homopolymer, a propylene-ethylene random copolymer, or a matrix of a propylene-1-butene random copolymer and an ethylene-propylene rubber copolymer in a reactor.

Preferably, the solvent extract content in the ethylene-propylene block copolymer may be 5 to 15% by weight. At this time, xylene is preferable as the solvent.

There is no particular limitation on the method for preparing the ethylene-propylene block copolymer, and a method for preparing an ethylene-propylene block copolymer known in the art to which the present invention pertains may be used as it is or modified appropriately. For example, using the Mitsui company's Hypol process, in which one or more bulk reactors and one or more gas phase reactors are connected in series to polymerize continuously, a method known to those skilled in the art is known. Ethylene-propylene block copolymers can be prepared by polymerization methods.

In a preferred embodiment of the present invention, the melt index (MI) of the polypropylene-based resin (A) may be 0.1 to 50 g/10 minutes when measured at 230° C. under a load of 2.16 kg based on ASTM D1238. When the melt index of the polypropylene resin (A) is less than 0.1 g/10 min, processability may deteriorate, and when the melt index exceeds 50 g/10 min, mechanical properties of molded articles, particularly films or sheets, may deteriorate. there is.

The polypropylene resin composition according to one embodiment of the present invention includes the polypropylene resin (A) in an amount of 95.0 to 99.0% by weight based on the total weight of components (A) and (B). If the content of the polypropylene-based resin (A) exceeds 99.0% by weight, it is difficult to obtain sufficient flame retardancy, and if the content is less than 95.0% by weight, mechanical properties of the molded article may deteriorate.

(B) non-halogen flame retardant

The flame retardant polypropylene resin composition according to an embodiment of the present invention includes a non-halogen flame retardant (B).

Here, the non-halogen flame retardant (B) is cyclohexane and peroxidized N-butyl-2,2,6,6-tetramethyl-4-piperidinamine-2,4,6-trichloro-1,3 1,3-propanediamine, N,N-1,2-ethanediylbis- combined with ,5-triazine reaction product, reaction product (1,3-propanediamine, N,N-1,2-ethanediylbis- , reaction products with cyclohexane and peroxidized N-butyl-2,2,6,6-tetramethyl-4-piperidinamine-2,4,6-trichloro-1,3,5-triazine reaction products; CAS No. 191680-81- 6) is.

The polypropylene resin composition according to one embodiment of the present invention, based on the total weight of components (A) and (B), contains a non-halogen flame retardant (B) in an amount of 0.5 to 5% by weight. If the content of the non-halogen flame retardant (B) is less than 0.5% by weight, the flame retardancy of the resin composition may be insufficient. On the other hand, when the content of the non-halogen flame retardant (B) exceeds 5% by weight, mechanical properties and productivity of the resin composition may deteriorate.

(C) transparent nucleating agent

In a preferred embodiment of the present invention, the flame retardant polypropylene resin composition is transparent, based on 100 parts by weight of components (A) and (B), (C) a sorbitol-based nucleating agent, a nonitol-based nucleating agent, and a mixture thereof selected from the group consisting of A nucleating agent may be further included in an amount of 500 to 10,000 ppm. The transparent nucleating agent serves to improve transparency by increasing visible light transmittance of the polypropylene resin composition and improve heat resistance and mechanical properties by increasing crystallinity. Economic efficiency may decrease.

In a preferred embodiment of the present invention, the sorbitol-based nucleating agent is benzylidenesorbitol, bisbenzylidenesorbitol, methylbenzylidenesorbitol, bismethylbenzylidenesorbitol, ethylenebenzylidenesorbitol, bisethylbenzylidenesorbitol, 3,4-dimethylbenzylidene consisting of sorbitol, 2-chloro-2,4-methylbenzylidenesorbitol, 1,3-chloro-2,4-methylbenzyl sorbitol and 1,3,2,4-bis-3,4-dimethylbenzylidenesorbitol It may be at least one selected from the group, but is not particularly limited thereto.

In a preferred embodiment of the present invention, the nonitol-based nucleating agent may be 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol; is not particularly limited to.

(D) additives

The polypropylene resin composition according to an embodiment of the present invention may further include an additive (D) within a range not departing from the scope of the present invention.

In a preferred embodiment of the present invention, the flame retardant polypropylene resin composition may further include an additive (D) in an amount of 2 parts by weight or less based on 100 parts by weight of components (A) and (B). In this case, the additive (D) may be at least one selected from the group consisting of antioxidants, neutralizers, reinforcing agents, fillers, weathering stabilizers, antistatic agents, lubricants, slip agents, pigments, and dyes, but is not limited thereto.

As a preferred embodiment, the flame retardant polypropylene resin composition according to an embodiment of the present invention may further include an antioxidant.

As the above antioxidants, phenol-based antioxidants, phosphite-based antioxidants, etc. may be used, specifically tetrakis (methylene (3,5-di-t-butyl-4-hydroxy) hydrosilyl nate), 1 One selected from the group consisting of ,3,5-trimethyl-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene and tris(2,4-di-t-butylphenyl)phosphite It may be more than one, but is not limited thereto.

At this time, the antioxidant may be added in an amount of 0.05 to 0.5 parts by weight, preferably 0.05 to 0.3 parts by weight, based on 100 parts by weight of components (A) and (B). If the content of the antioxidant is less than 0.05 parts by weight, it is difficult to secure the antioxidant effect of the resin. On the other hand, even if the content of the heat-resistant stabilizer exceeds 0.5 parts by weight, the increase in the antioxidant effect is insignificant, and the economic feasibility of the product may be reduced.

As a preferred embodiment, the polypropylene resin composition according to an embodiment of the present invention may further include a neutralizer.

The above neutralizing agent may be at least one selected from the group consisting of hydrotalcite and calcium stearate, but is not limited thereto.

At this time, the neutralizing agent may be added in an amount of 0.01 to 0.2 parts by weight, preferably 0.05 to 0.1 parts by weight, based on 100 parts by weight of components (A) and (B). If the content of the neutralizing agent is less than 0.01 parts by weight, it is difficult to ensure the effect of removing catalyst residues from the resin. On the other hand, even if the content of the neutralizer exceeds 0.2 parts by weight, the increase in the removal effect of the catalyst residue is insignificant and the cost-effectiveness of the resin composition may be reduced.

There is no particular limitation on the method for preparing the flame retardant polypropylene resin composition of the present invention, and a method for preparing a polypropylene resin composition known in the art to which the present invention pertains may be used as it is or modified appropriately, and each resin component and The compounds may be freely selected and mixed in a desired order without any particular order restriction.

Specifically, for example, each of the above-mentioned resins and compounds are mixed in a kneading machine such as a Henschel mixer, a kneader, a roll, or a Banbury mixer in the required amount for 1 to 2 hours, A polypropylene resin composition in the form of pellets may be prepared by melting and kneading at a temperature of 160 to 230 ° C. using a single-screw / twin-screw extruder.

According to another embodiment of the present invention, a polypropylene resin molded article manufactured by molding the flame retardant polypropylene resin composition of the present invention is provided.

There is no particular limitation on the method for preparing a molded article from the polypropylene resin composition according to the embodiment of the present invention, and a method known in the art to which the present invention pertains may be used. For example, a polypropylene resin molded article may be manufactured by molding the polypropylene resin composition according to an embodiment of the present invention by conventional methods such as extrusion molding, casting molding, and blown-film molding.

In a preferred embodiment of the present invention, the polypropylene resin molded article may be a film or sheet. At this time, the thickness of the film or sheet may be 40 to 150 μm, but is not particularly limited to this range.

In a preferred embodiment of the present invention, the polypropylene resin molded article may exhibit flame retardancy of UL-94 VTM-0 or higher and haze of 10% or less based on a thickness of 40 to 150 μm.

Example

Hereinafter, the present invention will be described in more detail through Examples and Comparative Examples. However, the following examples are only for exemplifying the present invention, and the scope of the present invention is not limited only to these.

Raw materials used in Examples and Comparative Examples are as follows.

A1: ethylene-propylene random copolymer resin (MI 5 g/10 min, melting temperature 150 ° C, solvent extract content 14% by weight)

A2: Ethylene-propylene random copolymer resin (MI 10 g/10 min, melting temperature 150 ° C, solvent extract content 4.3% by weight)

A3: propylene homopolymer resin (MI 9 g/10 min, melting temperature 160°C, solvent extract content 3.8% by weight)

A4: Ethylene-propylene block copolymer resin (MI 6 g/10 min, melting temperature 160 ° C, solvent extract content 15% by weight)

B1: flame retardant (cyclohexane and peroxidized N-butyl-2,2,6,6-tetramethyl-4-piperidinamine-2,4,6-trichloro-1,3,5-triazine reaction product 1,3-propanediamine combined with, N,N-1,2-ethanediylbis-, reaction product)

B2: flame retardant (aluminum hypophosphite)

B3: flame retardant (piperazine pyrophosphate)

C1: nucleating agent (1,3,2,4-bis-3,4-dimethylbenzylidenesorbitol)

C2: nucleating agent (1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol)

manufacturing example

Resins and compounds of the types and contents (unit: parts by weight) shown in Table 1 below were pelletized by melt blending at a temperature of about 220 ° C. in a twin screw extruder.

Subsequently, a film was prepared by a die casting molding method using Thermo Scientific HAAKE. At this time, the processing temperature was 190 ~ 210 ℃, the film thickness was 40 ~ 150 ㎛.

Example comparative example One 2 3 4 5 One 2 3 4 A1 99.3 - - - - - 90 - - A2 - 99 - 58 98.45 - - 92 - A3 - - 97 20 - - - - 98 A4 - - - 20 - 95 - - - B1 0.7 One 3 2 1.5 5 10 - - B2 - - - - - - - 8 - B3 - - - - - - - - 2 C1 - - - 0.6 0.05 - - - - C2 - - 0.5 - - - - - -

test example

The polypropylene resin compositions obtained in each of Examples and Comparative Examples and specimens prepared therefrom were tested in the following manner. The results are shown in Table 2 below.

(1) Melt index

It was measured with a load of 2.16 kg at 230° C. according to ASTM D1238.

(2) Density

Measured according to ASTM D 792.

(3) haze (%)

Haze was measured for 40 μm and 150 μm sheets according to the method of ASTM D1003.

(4) flame retardancy

For 40 μm and 150 μm sheets, measurements were made at room temperature according to UL 94 VTM Test (Thin Material Vertical Burning Test).

(5) flame retardant

Measured on 40 μm and 150 μm sheets in accordance with Fire and Disaster Management Notice No. 2021-7.

(6) Tensile strength and elongation

It was measured at room temperature by the method of ASTM D 638.

(7) Flexural modulus

Measured at 23° C. according to ASTM D770

(8) Izod impact strength

It was measured with a notched specimen having a thickness of 3.2 mm at 23° C. according to ASTM D256.

Example comparative example One 2 3 4 5 One 2 3 4 MI g/10 min 5 10 8 13 10 6 5 8 8 density g/cm 0.907 0.911 0.922 0.920 0.911 0.931 0.939 0.939 0.918 Cloudiness 40 μm 3.2 2.4 2.5 6.1 2.1 28.7 15.9 42.8 3.4 150 μm 4.5 3.9 4.7 9.6 3.5 40.6 33.4 75.7 5.4 flame retardant 40 μm VTM-0 VTM-0 VTM-0 VTM-0 VTM-0 VTM-0 VTM-0 VTM-2 NG 150 μm VTM-0 VTM-0 VTM-0 VTM-0 VTM-0 VTM-0 VTM-0 VTM-0 NG flame retardant 40 μm less than 40 less than 40 less than 40 less than 40 less than 40 less than 40 less than 40 less than 40 NG 150 μm less than 40 less than 40 less than 40 less than 40 less than 40 less than 40 less than 40 less than 40 NG The tensile strength MPa 26 27 35 29 26 30 23 26 35 elongation % 670 650 300 500 650 450 320 420 260 Flexural modulus MPa 900 700 1,600 1,100 700 1,200 950 720 1,600 Izod impact strength (23℃) kJ/㎡ 7.5 4 2.9 3.2 3.9 3 5 2.8 2.9

As confirmed from Tables 1 and 2 above, the polypropylene resin compositions of Examples falling within the scope of the present invention were excellent in both flame retardancy and transparency (haze).

On the other hand, in the case of Comparative Example 1 using the ethylene-propylene block copolymer alone as the polypropylene resin and Comparative Example 2 in which the content of the non-halogen flame retardant was out of the range of the present invention, the transparency of the resin composition was not good.

Further, in Comparative Examples 3 and 4 using a non-halogen flame retardant that does not fall within the scope of the present invention, transparency and/or flame retardancy of the resin composition were not good.

Therefore, the polypropylene resin composition according to the embodiment belonging to the scope of the present invention is excellent in both transparency and flame retardancy, and can be effectively used for films and sheets requiring transparency and flame retardancy.

Claims (12)

Based on the total weight of components (A) and (B), (A) 95.0 to 99.0% by weight of a polypropylene resin selected from propylene homopolymers, propylene-α-olefin random copolymers, and mixtures thereof; and (B) 0.5 to 5% by weight of a non-halogen flame retardant, wherein the non-halogen flame retardant is cyclohexane and peroxidized N-butyl-2,2,6,6-tetramethyl-4-piperidinamine 1,3-propanediamine combined with -2,4,6-trichloro-1,3,5-triazine reaction product, N,N-1,2-ethanediylbis-, flame retardant polypropylene as a reaction product resin composition.
The flame-retardant polypropylene resin composition according to claim 1, wherein the polypropylene-based resin (A) further comprises an ethylene-propylene block copolymer in an amount of 20% by weight or less based on the total weight of the polypropylene-based resin.
The flame retardant polypropylene resin composition according to claim 1, wherein the melt index of the polypropylene resin (A) is 0.1 to 50 g/10 minutes when measured at 230° C. under a load of 2.16 kg in accordance with ASTM D1238.
The method of claim 1, based on 100 parts by weight of components (A) and (B), (C) a transparent nucleating agent selected from the group consisting of sorbitol-based nucleating agents, nonitol-based nucleating agents, and mixtures thereof in an amount of 500 to 10,000 ppm Flame retardant polypropylene resin composition further comprising.
The method of claim 4, wherein the sorbitol-based nucleating agent is benzylidenesorbitol, bisbenzylidenesorbitol, methylbenzylidenesorbitol, bismethylbenzylidenesorbitol, ethylenebenzylidenesorbitol, bisethylbenzylidenesorbitol, 3,4-dimethylbenzylidenesorbitol, from the group consisting of 2-chloro-2,4-methyl benzylidenesorbitol, 1,3-chloro-2,4-methylbenzyl sorbitol and 1,3,2,4-bis-3,4-dimethylbenzylidenesorbitol At least one selected flame retardant polypropylene resin composition.
The flame-retardant polypropylene resin composition according to claim 4, wherein the nonitol-based nucleating agent is 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol. .
The method of claim 1, based on 100 parts by weight of components (A) and (B), further comprising an additive (D) in an amount of 2 parts by weight or less, wherein the additive (D) is an antioxidant, a neutralizer, a reinforcing agent, a filler, A flame retardant polypropylene resin composition comprising at least one selected from the group consisting of weathering stabilizers, antistatic agents, lubricants, slip agents, pigments and dyes.
The method of claim 7, wherein the additive (D) is pentaerythritol tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate), 1,3,5-trimethyl-tris ( Flame retardant polypropylene resin which is at least one antioxidant selected from the group consisting of 3,5-di-t-butyl-4-hydroxybenzyl)benzene and tris(2,4-di-t-butylphenyl)phosphite composition.
The flame retardant polypropylene resin composition according to claim 7, wherein the additive (D) is at least one neutralizing agent selected from the group consisting of hydrotalcite and calcium stearate.
A flame retardant polypropylene resin molded article prepared by molding the polypropylene resin composition according to any one of claims 1 to 9.
The flame-retardant polypropylene resin molded article according to claim 10, which is a film or a sheet.
The flame retardant polypropylene resin molded article according to claim 10, which exhibits flame retardancy of UL-94 VTM-0 or higher and haze of 10% or less based on a thickness of 40 to 150 μm.