Patent Description:
Heat sealable and easy-opening films are employed on a large scale for temporarily closing containers that include, for example, food products. During use, a consumer tears away the peelable film. To gain consumer acceptance, a number of characteristics associated with a heat sealable and peelable film are desired.

Heat sealable films must be capable of being sealed upon the application of heat. During typical sealing processes, the backing or web layer of the film comes into direct contact with a heated surface such as a sealing jaw. Heat is thus transferred through the backing layer of the film to melt and fuse the inner sealant layer to form a seal. Accordingly the backing layer generally has a higher melting temperature than the inner sealant layer so that the backing layer of the film does not substantially melt and therefore does not stick to the heated surface.

To have a low heat seal initiation temperature is desirable for the reason that it helps to ensure fast packaging line speeds and a broad sealing window which could accommodate variability in process conditions, such as pressure and temperature. A broad sealing window also enables high speed packaging of heat sensitive products, as well as, provides a degree of forgiveness for changes in packaging or filling speeds.

It also desirable that the pealing force at room temperature be not too high so that the film can be pealed manually.

Thus there are two different needs, a low sealing temperature for packaging line speed and a right peeling force at room temperature for easy pealing.

<CIT> described a composition suitable for use as a peelable seal layer comprising from <NUM> to <NUM> wt% of a propylene based polymer and from <NUM> to <NUM> wt% of a secondo polymer which has interfacial adhesion with the first polymer of less than <NUM> N/mm.

The applicant found that it is possible to obtain an improved curve sealing temperature-peeling force by using a composition of <NUM>-butene based copolymer, in order to achieve a lower sealing initiation temperature.

Thus an object of the present disclosure is a polymer composition comprising a <NUM>-butene copolymer, said composition comprising:.

Thus an object of the present disclosure is a <NUM>-butene copolymer composition comprising:.

The term "copolymer" as used in the present patent application refers to polymers containing only two comonomers such as propylene and ethylene or <NUM>-butene and ethylene.

Preferably component A) has the following features:.

Component A) can optionally contains from <NUM>. 5wt% to <NUM> wt%; preferably from <NUM> wt% to <NUM> wt% of a masterbatch such as Premix Antiblocking PP45.

The <NUM>-butene copolymer composition of the present disclosure can be advantageously used for the preparation of films, in particular multilayer films wherein the sealing layer comprises the <NUM>-butene copolymer composition of the present disclosure.

Thus a further object of the present disclosure is a film comprising the <NUM>-butene copolymer composition of the present disclosure in particular a further object of the present disclosure is a multilayer film wherein the sealing layer comprises the <NUM>-butene copolymer composition of the present disclosure.

The multilayer films of the present disclosure are characterized by having at least the sealing layer comprising the <NUM>-butene copolymer composition of the present disclosure. The remaining layers can be formed of any material known in the art for use in multilayer films or in laminated products. Thus, for example, each layer can be formed of a polypropylene homopolymer or copolymer or polyethylene homopolymer or copolymer or other kind of polymers such as EVA.

The combination and number of the layers of the multilayer structure is not particularly limited. The number is usually from <NUM> to <NUM> layers or even more, preferably <NUM> to <NUM> layers, and more preferably <NUM> to <NUM> layers, and more preferably <NUM> to <NUM> layers and combinations including C/B/A, C/B/C/B/A, C/B/C/D/C/B/A are possible, provided that at least one sealing layer A comprises the <NUM>-butene copolymer composition of the present disclosure.

Preferred layers of the multilayer film of the present disclosure are <NUM> or <NUM> wherein at sealing layer comprises, preferably consists essentially of the <NUM>-butene copolymer composition of the present disclosure. Wherein the term "consists essentially of" means that specific further components can be present, namely those not materially affecting the essential characteristics of the compound or composition. In particular no further polymers are present in the composition.

The <NUM>-butene copolymer composition of the present disclosure can be prepared by mechanically blend component A) and component B) in accordance with processes well known in the art.

Component A) and component B) are commercially available in the market.

Component B) is a <NUM>-butene ethylene copolymer commercially available, such as Koattro DP <NUM> sold by LyondellBasell.

The <NUM>-butene copolymer composition of the present disclosure can further contain additives used in the art.

The <NUM>-butene copolymer composition of the present disclosure can be advantageously used as sealing layer in a multilayer film, it allows to obtain the same peeling force at lower sealing temperature, so that the processability of the final container to which the sealing film is applied results to be improved.

The following examples are given to illustrate but not limit the present disclosure.

Melt Flow Rate: measured according to ISO <NUM> - <NUM> (<NUM>, <NUM> or <NUM>, <NUM>).

Tensile Modulus was measured according to ISO <NUM>-<NUM>, and ISO <NUM>-<NUM> on injection moulded sample.

Density was measured according to ISO <NUM>-<NUM>.

The density of samples was measured according to ISO <NUM>-<NUM> (ISO <NUM>-<NUM> method A "Methods for determining the density of non-cellular plastics- Part <NUM>: Immersion method, liquid pyknometer method and titration method"; Method A: Immersion method, for solid plastics (except for powders) in void-free form). Test specimens were taken from compression moulded plaques conditioned for <NUM> days before carrying out the density measure.

Flexural Modulus according to ISO <NUM>, and supplemental conditions according to ISO <NUM>-<NUM>.

Melting temperature was measured according ISO <NUM>-<NUM>.

<NUM>C NMR spectra were acquired on a Bruker AV-<NUM> spectrometer equipped with cryoprobe, operating at <NUM> in the Fourier transform mode at <NUM>. Ethylene has been measured on the total composition. The ethylene content of component B) has been calculated by using the amount of component B) according to the following equation: <MAT>.

The samples were dissolved in <NUM>,<NUM>,<NUM>,<NUM>-tetrachloroethane-d2 at <NUM> with an <NUM>% wt/v concentration. Each spectrum was acquired with a <NUM>° pulse, <NUM> seconds of delay between pulses and CPD to remove <NUM>H-<NUM>C coupling. <NUM> transients were stored in <NUM> data points using a spectral window of <NUM>.

The peak of the Sββ carbon (nomenclature according to "<NPL>) was used as an internal reference at <NUM> ppm. The samples were dissolved in <NUM>,<NUM>,<NUM>,<NUM>-tetrachloroethane-d2 at <NUM> with a <NUM> % wt/v concentration. Each spectrum was acquired with a <NUM>° pulse, and <NUM> seconds of delay between pulses and CPD to remove <NUM>H-<NUM>C coupling. <NUM> transients were stored in <NUM> data points using a spectral window of <NUM>.

The assignments of the spectra, the evaluation of triad distribution and the composition were made according to Kakugo ("<NPL>) using the following equations: <MAT> <MAT> <MAT>.

The molar percentage of ethylene content was evaluated using the following equation:.

E% mol = <NUM> * [PEP+PEE+EEE]The weight percentage of ethylene content was evaluated using the following equation: <MAT> <MAT>
where P% mol is the molar percentage of propylene content, while MWE and MWP are the molecular weights of ethylene and propylene, respectively.

The product of reactivity ratio r1r2 was calculated according to Carman (C. Harrington and C. Wilkes, Macromolecules, <NUM>; <NUM>, <NUM>) as: <MAT>.

The tacticity of Propylene sequences was calculated as mm content from the ratio of the PPP mmTββ (<NUM>-<NUM> ppm) and the whole Tββ (<NUM>-<NUM> ppm).

The ethylene content of component B) has been calculated from the total ethylene content by using the following equation:
<MAT>.

Wherein E%wt total is the total ethylene content E%wt/B is the ethylene content of component B) and wt%B is the amount (wt%/<NUM>) of component B).

The content of comonomers was determined by infrared spectroscopy by collecting the IR spectrum of the sample vs. an air background with a Fourier Transform Infrared spectrometer (FTIR). The instrument data acquisition parameters were:.

Sample Preparation - Using a hydraulic press, a thick sheet was obtained by compression molding about g <NUM> of sample between two aluminum foils. A small portion was cut from this sheet to mold a film. The film thickness was set in order to have a maximum absorbance of the CH<NUM> absorption band recorded at ~<NUM>-<NUM> of <NUM> a. (% Transmittance > <NUM>%). Molding conditions were <NUM>±<NUM> (<NUM>°F) and pressure was around <NUM>/cm<NUM> (<NUM> PSI) for about one minute. The pressure was then released, the sample removed from the press and cooled to room temperature. The spectrum of pressed film sample was recorded in absorbance vs. wavenumbers (cm-<NUM>). The following measurements were used to calculate ethylene (C<NUM>) and <NUM>-butene (C<NUM>) contents:.

The ratio AC2 / At is calibrated by analyzing ethylene-<NUM>-butene standard copolymers of known compositions, determined by NMR spectroscopy. In order to calculate the ethylene (C<NUM>) and <NUM>-butene (C<NUM>) content, calibration curves were obtained by using samples of known amount of ethylene and <NUM>-butene detected by <NUM>C-NMR.

Calibration for ethylene - A calibration curve was obtained by plotting AC2/At versus ethylene molar percent (%C2m), and the coefficient aC2, bC2 and cC2 then calculated from a "linear regression".

Calibration for <NUM>-butene - A calibration curve was obtained by plotting FCRca/Ac versus butane molar percent (%Cam) and the coefficients aC4, bC4 and CC4 then calculated from a "linear regression".

The spectra of the unknown samples are recorded and then (At), (AC2) and (FCRC4) of the unknown sample are calculated.

The ethylene content (% molar fraction C2m) of the sample was calculated as follows: <MAT>.

The <NUM>-butene content (% molar fraction C4m) of the sample was calculated as follows: <MAT> aC4, bC4, cC4 aC2, bC2, cC2 are the coefficients of the two calibrations.

Changes from mol% to wt% are calculated by using molecular weights.

Component A contains: <NUM> wt% of Clyrell RC <NUM> a random propylene ethylene copolymer; <NUM> wt% of Lupolen <NUM> a linear low density polyethylene; <NUM> wt% of PB <NUM> a <NUM>-butene homopolymer all commercial grades sold by Lyondellbasell, <NUM> wt% masterbatch and <NUM> wt% standard additives.

Component B is a commercial product sold by Lyondelbasell under the tradename Koattro DP <NUM>.

The features of components A are reported on table <NUM>.

The features of components A and B are reported on table <NUM>.

Component A has been blended with component B (85wt% A; <NUM> wt% B) and a <NUM> micron cast film has been obtained. The cast film has been sealed at different sealing temperature on itself. For each sealing temperature the peeling force has been measured.

In comparative example <NUM> the blend of <NUM> wt% of A and <NUM> wt% of B has been replaced with <NUM> wt% of A.

Table <NUM> shows the peeling forces at various sealing temperatures.

Claim 1:
A polymer composition comprising a <NUM>-butene copolymer, said composition comprising:
A) from <NUM> wt% to <NUM> wt% of a polymer composition (A) comprising:
A1) From <NUM> wt% to <NUM> wt% of a propylene ethylene copolymer having:
i) a Melt Flow Rate: measured according to ISO <NUM>-<NUM> -(<NUM>, <NUM>) ranging from <NUM> to <NUM>/<NUM>;
ii) density measured according to ISO <NUM>-<NUM> ranging from <NUM>/cm<NUM> to <NUM>/cm<NUM>;
iii) flexural modulus measured according to ISO <NUM> ranging from <NUM> MPa to <NUM> MPa;
iv) ethylene content ranging from <NUM> wt% to <NUM> wt%;
A2) from <NUM> wt% to <NUM> wt% of a low density polyethylene having:
i) a Melt Flow Rate: measured according to ISO <NUM>-<NUM> (<NUM>, <NUM>) ranging from <NUM> to <NUM>/<NUM>;
ii) density measured according to ISO <NUM>-<NUM> ranging from <NUM>/cm<NUM> to <NUM>/cm<NUM>;
iii) tensile modulus measured according to ISO <NUM>-<NUM> ranging from <NUM> MPa to <NUM> MPa;
A3) from <NUM> wt% to <NUM> wt% of a <NUM>-butene homopolymer having:
i) a Melt Flow Rate: measured according to ISO <NUM>-<NUM> (<NUM>, <NUM>) ranging from <NUM> to <NUM>/<NUM>;
ii) density measured according to ISO <NUM>-<NUM> ranging from <NUM>/cm<NUM> to <NUM>/cm<NUM>;
iii) flexural modulus measured according to ISO <NUM> ranging from <NUM> MPa to <NUM> MPa;
the sum of the amounts of A1, A2 and A3 being <NUM> wt%;
B) from <NUM> wt% to <NUM> wt% of of a copolymer of <NUM>-butene and ethylene containing from <NUM> wt% to <NUM> wt% of ethylene derived units; said copolymer of <NUM>-butene and ethylene having:
- a Melt Flow Rate: measured according to ISO <NUM>-<NUM> -(<NUM>, <NUM>) ranging from <NUM> to <NUM>/<NUM>;
- Flexural modulus measured according to ISO <NUM> ranging from <NUM> MPa to <NUM> MPa;
- The melting temperature measured according to Iso <NUM>-<NUM> ranging from <NUM> and <NUM>, form I
the sum of the amounts of A) and B) being <NUM> wt%.