Polypropylene film

Abstract

The invention relates to a film comprising a polypropylene composition comprising an ethylene-propylene-1-butene terpolymer which comprises a) units derived from ethylene in an amount of 2.2 to 3.5 wt% with respect to the total ethylene-propylene-1-butene terpolymer; b) units derived from propylene in an amount of 91.0 to 94.0 wt% with respect to the total ethylenepropylene-1-butene terpolymer; and c) units derived from 1-butene in an amount of 3.3 to 8.5 wt% with respect the total ethylene-propylene-1-butene terpolymer

Description

[0001] POLYPROPYLENE FILM

[0002] The present invention relates to a film comprising a composition comprising an ethylene-propylene-1 -butene terpolymer.

[0003] It is desirable for a packaging film to have a low sealing initiation temperature (SIT). It is known to make a film from an ethylene-propylene-1 -butene terpolymer.

[0004] W02009019169A1 discloses a film comprising at least one layer comprising a propylene terpolymer comprising comonomer units derived from ethylene and one alpha-olefin selected from the group of C4-C8 alpha-olefins and being characterized by

[0005] - a xylene soluble fraction higher than 9% wt;

[0006] - a total content of comonomer units not less than 8% wt;

[0007] - a ratio of ethylene to the C4-C8 alpha-olefins ranging from 0.1 to 0.8; and

[0008] - a melting temperature Tm higher than or equal to (28.013X+120.5), where X is the value of the ratio of ethylene to the C4-C8 alpha-olefins.

[0009] WO2022167368A1 discloses a film made from a blend obtainable by compounding an ethylene-propylene-1 -butene terpolymer base resin and a propylene butene random copolymer upgrading resin. The ethylene-propylene-1 -butene terpolymer base resin includes a) units derived from ethylene in an amount of 0.1 to 2.0 wt.-%, b) units derived from propylene in an amount of 88.0 to 95.9 wt.-% and c) units derived from butene in an amount of 4.0 to 10.0 wt.-%. The film has a sealing initiation temperature (SIT) below 106°C.

[0010] It is an objective of the present invention to provide a film having a low sealing initiation temperature (SIT) and good mechanical properties such as tensile properties, impact resistance and tear resistance.

[0011] Accordingly, the invention provides a film comprising a polypropylene composition comprising an ethylene-propylene-1 -butene terpolymer which comprises a) units derived from ethylene in an amount of 2.2 to 3.5 wt% with respect the total ethylene-propylene-1 -butene terpolymer; b) units derived from propylene in an amount of 91 .0 to 94.0 wt% with respect the total ethylenepropylene- 1 -butene terpolymer base resin; and c) units derived from butene in an amount of 3.3 to 8.5 wt% with respect the total ethylene-propylene-1 -butene terpolymer base resin.

[0012] It was surprisingly found that the film according to the invention has a low SIT and good mechanical properties such as tensile properties, impact resistance and tear resistance.

[0013] Ethylene-propylene-1 -butene terpolymer

[0014] The total amount of units derived from ethylene, propylene and butene is 100 wt% of the terpolymer.

[0015] Preferably, the amount of a) units derived from ethylene is 2.3 to 3.4 wt% with respect the total ethylene-propylene-1 -butene terpolymer.

[0016] Preferably, the amount of b) units derived from propylene is 91 .5 to 93.9 wt%, more preferably 92.0 to 93.7 wt%, more preferably 92.5 to 93.5 wt%, with respect the total ethylene-propylene-1 -butene terpolymer.

[0017] Preferably, the amount of c) units derived from butene is 3.3 to 7.5 wt%, more preferably 3.3 to 6.5 wt%, more preferably 3.4 to 5.5 wt%, with respect the total ethylene-propylene-1 -butene terpolymer.

[0018] In some preferred embodiments, the amount of a) units derived from ethylene is less than 2.9 wt% with respect the total ethylene-propylene-1 -butene terpolymer and / or the amount of c) units derived from butene is 4.0 to 7.5 wt%, preferably 4.0 to 6.5 wt%, more preferably 4.0 to 5.5 wt%, with respect the total ethylene-propylene-1 -butene terpolymer.

[0019] In some preferred embodiments, the amount of a) units derived from ethylene is 2.3 to 2.8 wt% with respect the total ethylene-propylene-1 -butene terpolymer and / or the amount of b) units derived from propylene is 92.5 to 93.5 wt% with respect the total ethylene-propylene-1 -butene terpolymer and / or the amount of c) units derived from butene is 4.2 to 5.0 wt% with respect the total ethylene-propylene-1 -butene terpolymer.

[0020] In some preferred embodiments, the amount of a) units derived from ethylene is at least 2.9 wt% with respect the total ethylene-propylene-1 -butene terpolymer and / or the amount of c) units derived from butene is less than 4.0 wt% with respect the total ethylene-propylene-1 -butene terpolymer.

[0021] In some preferred embodiments, the amount of a) units derived from ethylene is 3.0 to 3.4 wt% with respect the total ethylene-propylene-1 -butene terpolymer and / or the amount of b) units derived from propylene is 92.5 to 93.5 wt% with respect the total ethylene-propylene-1 -butene terpolymer and / or the amount of c) units derived from butene is 3.4 to 3.9 wt% with respect the total ethylene-propylene-1 -butene terpolymer.

[0022] Amounts of units derived from ethylene, propylene and butene in the terpolymer are determined by13C NMR, e.g. as follows:

[0023] The sample is dissolved at 130°C in C2D2CI4 containing DBPC as stabilizer. The NMR spectra is recorded on a Bruker Avance500 spectrometer equipped with a cryogenically cooled probe head operating at 125°C.

[0024] Preferably, the terpolymer has a melt flow index measured according to IS01133- 1 :2011 at 2.16 kg and 230 °C of 1.0 to 20 dg / min, preferably 3.0 to 15 dg / min, more preferably 6.0 to 10 dg / min. This allows the terpolymer to be made into a film in an efficient manner.

[0025] Preferably, the terpolymer has Mw / Mn of 5.0 to 10.0, preferably 5.5 to 7.5, more preferably 6.0 to 7.0, wherein Mw and Mn are determined in accordance with ASTM D6474-12.

[0026] Mw stands for the weight average molecular weight and Mn stands for the number average weight.

[0027] Preferably, the terpolymer has a xylene soluble fraction determined according to ISO ISO16152:2005 at 25 °C of 5.0 to 10.5 wt%, more preferably 7.0 to 9.0 wt%. Low xylene soluble fraction is advantageous for the processing of the polypropylene composition into film in that contamination of the die by the migration of the xylene soluble fraction is reduced.

[0028] Preferably, the terpolymer has a melting temperature Tm of 130 to 140 °C, preferably 133 to 138 °C. Such relatively high melting temperature allows for efficient processing of the polypropylene composition for making the film according to the invention. Melting temperature Tm can be determined by differential scanning calorimetry (DSC) by heating a sample of 5 mg from room temperature to 200 °C at a rate of 10 °C / min, holding at 200 °C for 5 mins, then cooling to room temperature at a rate of 10 °C / min, then heating to 200 °C at a rate of 10 °C / min, wherein the melting temperature is taken from the second temperature increase.

[0029] Preferably, the terpolymer has Vicat softening temperature (VST) of 110 to 120 °C determined according to ISO 306 using a force of 10N and a heating rate of 120 °C / h.

[0030] Polymerization of a terpolymer of ethylene, propylene and butene is described e.g. in W02009019169. The skilled person can obtain the terpolymer used according to the invention by adjusting the conditions of the process described in W02009019169, e.g. by adjusting the monomer feeds.

[0031] In some preferred embodiments, the amount of the terpolymer in the polypropylene composition is at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.5 wt%, at least 99.9 wt% or 100 wt% with respect to the total polymer composition.

[0032] In some embodiments, the composition may further comprise a further polymer selected from the group consisting of polyolefin based elastomers, polyolefin based plastomers and polyethylenes and combinations thereof. The further polymer may be an elastomer of ethylene and a-olefin comonomer having 4 to 8 carbon atoms, for example an ethylene-butene copolymer, an ethylene-hexene copolymer an ethyleneoctene copolymer. The further polymer may have a density of 0.850-0.915 g / cm3. The amount of said further polymer may e.g. be 1 .0 to 30 wt%, wherein the total amount of the terpolymer and the further polymer is at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.5 wt%, at least 99.9 wt% or 100 wt% with respect to the total polypropylene composition.

[0033] Additives

[0034] The polypropylene composition of the present invention may optionally include additives which do not interfere with the previously mentioned desirable properties but enhance other favorable properties. Optional additives that may be compounded or blended into the composition of the invention in customary amounts include stabilisers, e.g. heat stabilisers, anti-oxidants, UV stabilizers; clarifiers; surface tension modifiers and lubricants.

[0035] The amount of the additives may e.g. be 0.0 to 5.0 wt%, for example 0.1 to 1.0 wt%, with respect to the total polypropylene composition. Preferably, the total amount of polymers (propylene terpolymer and optional further polymer) and the additives is 100 wt% of the total polypropylene composition. Preferably, the total amount of the propylene terpolymer and the additives is 100 wt% of the total polypropylene composition.

[0036] The polypropylene composition can be formed into the film according to the invention by known methods. The film according to the invention can be a cast film or a blown film, preferably a cast film.

[0037] Preferably, the amount of the polypropylene composition with respect to the film is at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.5 wt%, at least 99.9 wt% or 100 wt%.

[0038] The invention further provides a packaging comprising the film according to the invention. The packaging may e.g. be a tea packaging, a cloth packaging, a napkin packaging, a packaging of a box containing articles such as a cell phone or a toy.

[0039] The invention further provides use of the film according to the invention for making a packaging, for example use of the film according to the invention in a tea packaging, a cloth packaging, a napkin packaging, a packaging of a box containing articles a cell phone or a toy.

[0040] It is noted that the invention relates to the subject-matter defined in the independent claims alone or in combination with any possible combinations of features described herein, preferred in particular are those combinations of features that are present in the claims. It will therefore be appreciated that all combinations of features relating to the composition according to the invention; all combinations of features relating to the process according to the invention and all combinations of features relating to the composition according to the invention and features relating to the process according to the invention are described herein. It is further noted that the term ‘comprising’ does not exclude the presence of other elements. However, it is also to be understood that a description on a product / composition comprising certain components also discloses a product / composition consisting of these components. The product / composition consisting of these components may be advantageous in that it offers a simpler, more economical process for the preparation of the product / composition. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps. The process consisting of these steps may be advantageous in that it offers a simpler, more economical process.

[0041] When values are mentioned for a lower limit and an upper limit for a parameter, ranges made by the combinations of the values of the lower limit and the values of the upper limit are also understood to be disclosed.

[0042] The invention is now elucidated by way of the following examples, without however being limited thereto.

[0043] Experiments

[0044] Terpolymers shown in Table 1 were used. Terpolymers in CEx 1 , Ex 2, CEx 4 and Ex 6 were produced by Spherizone technology. Terpolymer in CEx 3 was produced by Spheripol technology and terpolymer in CEx 5 was produced by Innovene technology.

[0045] The amounts of units derived from ethylene, butene and propylene in the terpolymer as well as Mw / Mn, xylene soluble fraction, MFI, Tm and VST of the terpolymers were determined and are shown in Table 1.

[0046] Amounts of units derived from ethylene, butene and propylene in the terpolymer were determined by 13C NMR: The sample was dissolved at 130°C in C2D2CI4 containing DBPC as stabilizer. The NMR spectra was recorded on a Bruker Avance500 spectrometer equipped with a cryogenically cooled probe head operating at 125°C.

[0047] Mw and Mn were determined in accordance with ASTM D6474-12 (Standard Test Method for Determining Molecular Weight Distribution and Molecular Weight Averages of Polyolefins by High Temperature Gel Permeation Chromatography). Mw stands for the weight average molecular weight and Mn stands for the number average weight. The measurement was performed using a configuration in which a Polymer Char IR5 infrared concentration detector and a Polymer Char online viscosity detector were used to gain ‘absolute’ or accurate molar masses. Three columns of Polymer Laboratories 13 pm PLgel Olexis, 300 x 7.5 mm (3 x Agilent PLgel Olexis 13pm, 7.5 x 300mm columns) were used in series with 1 ,2,4-trichlorobenzene stabilized with 1 g / L butylhydroxytoluene (also known as 2,6-di-fert-butyl-4-methylphenol or BHT) as eluent. The molar mass was determined based on a calibration using linear PE standards (narrow and broad (Mw / Mn = 4 to 15)) in the range of 0.5 - 2800 kg / mol.

[0048] Xylene soluble fraction was determined according to 18016152:2005. 2g of pellet sample is dissolved in 200 ml xylene under reflux conditions, then cooled under controlled conditions and maintained at 25 °C for 30 minutes to ensure controlled crystallization of the insoluble fraction. The xylene soluble fraction is then recovered by evaporation of 100 ml aliquot of the filtrate and determined by weighing the residue.

[0049] MFI was determined according to ISO1133-1 (2011) at 230 °C and 2.16 kg.

[0050] Melting temperature Tm was determined by differential scanning calorimetry (DSC) by heating a sample of 5 mg from room temperature to 200 °C at a rate of 10 °C / min, holding at 200 °C for 5 mins, then cooling to room temperature at a rate of 10 °C / min, then heating to 200 °C at a rate of 10 °C / min, wherein the melting temperature is taken from the second temperature increase.

[0051] Vicat softening temperature (VST) was determined according to ISO 306 using a force of 10N and a heating rate of 120 °C / h.

[0052] The terpolymer was mixed with an additive package consisting of Irganox 1010, Irgafos 168, slipping agent (erucamide), anti-blocking agent (SiO2) and acid scavenger to obtain a composition to be used for film casting. A film having a thickness of 30 pm was prepared by casting the composition according to the following conditions:

[0053] The transmission, haze, SIT, hot tack and various mechanical properties were measured on the obtained films and are shown in Table 2.

[0054] Transmission was determined according to ASTM D1003.

[0055] Haze was determined according to ASTM D1003.

[0056] SIT was determined according to ASTM F88 wherein the sealing procedure was performed with dwell time of 1s, seal pressure of 0.3 MPa and conditioning of at least 40 h at 23 °C, 50%RH. The lowest temperature at which the max force of at least 2.5 N 1 15 mm was obtained is determined as the SIT.

[0057] Hot tack was determined according to ASTM F1921 wherein the sealing procedure was performed with seal time 1s, seal pressure 0.3 MPa and cooling time 0.3s and separate rate of 200 mm / s. Maximum force is determined as the hot tack.

[0058] Tensile modulus (MD and TD) was determined according to ASTM D882 at 23°C

[0059] Protrusion puncture resistance was determined according to ASTM D5748-95 at 23°C and testing speed of 250 mm / min .

[0060] Impact resistance was determined by ASTM D1709 method A.

[0061] Elmendorf tear resistance was determined according to ASTM D1922. Table 1

[0062] It can be understood that the film according to the invention has the combination of low SIT, high hot tack and good mechanical properties.

Claims

CLAIMS1 . A film comprising a polypropylene composition comprising an ethylene-propylene- 1 -butene terpolymer which comprises a) units derived from ethylene in an amount of 2.2 to 3.5 wt% with respect to the total ethylene-propylene-1 -butene terpolymer; b) units derived from propylene in an amount of 91 .0 to 94.0 wt% with respect to the total ethylenepropylene- 1 -butene terpolymer; and c) units derived from 1 -butene in an amount of 3.3 to 8.5 wt% with respect the total ethylene-propylene-1 -butene terpolymer.

2. The film according to any one of the preceding claims, wherein the terpolymer has a melt flow index measured according to ISO1133-1 :2011 at 2.16 kg and 230 °C of 1 .0 to 20 dg / min, preferably 3.0 to 15 dg / min, more preferably 6.0 to 10 dg / min.

3. The film according to any one of the preceding claims, wherein the terpolymer has Mw / Mn of 5.0 to 10.0, preferably 5.5 to 7.5, more preferably 6.0 to 7.0.

4. The film according to any one of the preceding claims, wherein the terpolymer has a xylene soluble fraction determined according to 18016152:2005 at 25 °C of 5.0 to 10.5 wt%, preferably 7.0 to 9.0 wt%.

5. The film according to any one of the preceding claims, wherein the terpolymer has a melting temperature of 130 to 140 °C, preferably 133 to 138 °C, determined by differential scanning calorimetry.

6. The film according to any one of the preceding claims, wherein the terpolymer has a Vicat softening temperature (VST) of 110 to 120 °C determined according to ISO 306 using a force of 10N and a heating rate of 120 °C / h.

7. The film according to any one of the preceding claims, wherein the amount of a) units derived from ethylene is 2.3 to 3.4 wt% with respect the total ethylene-propylene-1 -butene terpolymer and / or the amount of b) units derived from propylene is 91 .5 to 93.9 wt%, preferably 92.0 to 93.7 wt%, more preferably 92.5 to 93.5 wt%, with respect the total ethylene- propylene-1 -butene terpolymer and / orthe amount of c) units derived from butene is 3.3 to 7.5 wt%, preferably 3.3 to 6.5 wt%, more preferably 3.4 to 5.5 wt%, with respect the total ethylene-propylene-1 - butene terpolymer.

8. The film according to any one of claims 1 to 7, wherein the amount of a) units derived from ethylene is less than 2.9 wt% with respect the total ethylene-propylene-1 -butene terpolymer and the amount of c) units derived from butene is 4.0 to 7.5 wt%, preferably 3.3 to 6.5 wt%, more preferably 3.4 to 5.5 wt%, with respect the total ethylene-propylene-1 - butene terpolymer.

9. The film according to claim 8, wherein the amount of a) units derived from ethylene is 2.3 to 2.8 wt% with respect the total ethylene-propylene-1 -butene terpolymer, the amount of b) units derived from propylene is 92.5 to 93.5 wt% with respect the total ethylene-propylene-1 -butene terpolymer and the amount of c) units derived from butene is 4.2 to 5.0 wt% with respect the total ethylene-propylene-1 -butene terpolymer.

10. The film according to any one of claims 1 to 7, wherein the amount of a) units derived from ethylene is at least 2.9 wt% with respect the total ethylene-propylene-1 -butene terpolymer and the amount of c) units derived from butene is less than 4.0 wt% with respect the total ethylene-propylene-1 -butene terpolymer.11 . The film according to claim 10, wherein the amount of a) units derived from ethylene is 3.0 to 3.4 wt% with respect the total ethylene-propylene-1 -butene terpolymer, the amount of b) units derived from propylene is 92.5 to 93.5 wt% with respect the total ethylene-propylene-1 -butene terpolymer and the amount of c) units derived from butene is 3.4 to 3.9 wt% with respect the total ethylene-propylene-1 -butene terpolymer.

12. The film according to any one of the preceding claims, wherein the amount of the terpolymer with respect to the total polypropylene composition is at least 95 wt%, atleast 98 wt%, at least 99 wt%, at least 99.5 wt%, at least 99.9 wt% or 100 wt% with respect to the total polypropylene composition.

13. The film according to any one of the preceding claims, wherein the amount of the polypropylene composition with respect to the film is at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.5 wt%, at least 99.9 wt% or 100 wt%14. The film according to any one of the preceding claims, wherein the film is a cast film or a blown film, preferably a cast film.

15. A packaging comprising the film according to any one of the preceding claims.

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