BE1025023B1 - Improved multilayer shrink film and method of manufacturing - Google Patents

Abstract

The present invention relates to a multilayer shrink film for packaging goods, and a method for manufacturing them. The multilayer shrink film comprises an outer layer, an inner layer and an intermediate layer positioned between the outer layer and the inner layer. Each of the outer, inner and intermediate layers comprises low density polyethylene and the same internal antistatic additive. The weight percentage of the antistatic additive is higher in the intermediate layer than in each of the outer and inner layer.

Description

Priority date:

International classification: B32B 7/02, B32B 27/08, B32B 27/32 Application number: BE2017 / 5606

Date of submission: 31/08/2017

Holder:

SEGERS & BALCAEN NV 1770, LIEDEKERKE Belgium

Inventor:

BALCAEN Paul 1770 LIEDERKERKE Belgium

Improved multilayer shrink film and method of manufacturing it

The present invention relates to a multilayer shrink film for packaging goods and a method of manufacturing it. The multilayer shrink film includes an outer layer, an inner layer and an intermediate layer positioned between the outer layer and the inner layer. Each of the outer, inner and intermediate layers includes low density polyethylene and the same internal antistatic additive. The weight percentage of the anti-static additive is higher in the intermediate layer than in each of the outer and inner layers.

BELGIAN INVENTION PATENT

FPS Economy, K.M.O., Self-employed & Energy

Publication number: 1025023 Filing number: BE2017 / 5606

Intellectual Property Office

International Classification: B32B 7/02 B32B 27/08 B32B 27/32 Date of Grant: 26/09/2018

The Minister of Economy,

Having regard to the Paris Convention of 20 March 1883 for the Protection of Industrial Property;

Having regard to the Law of March 28, 1984 on inventive patents, Article 22, for patent applications filed before September 22, 2014;

Having regard to Title 1 Invention Patents of Book XI of the Economic Law Code, Article XI.24, for patent applications filed from September 22, 2014;

Having regard to the Royal Decree of 2 December 1986 on the filing, granting and maintenance of inventive patents, Article 28;

Having regard to the application for an invention patent received by the Intellectual Property Office on 31/08/2017.

Whereas for patent applications that fall within the scope of Title 1, Book XI, of the Code of Economic Law (hereinafter WER), in accordance with Article XI.19, § 4, second paragraph, of the WER, the granted patent will be limited. to the patent claims for which the novelty search report was prepared, when the patent application is the subject of a novelty search report indicating a lack of unity of invention as referred to in paragraph 1, and when the applicant does not limit his filing and does not file a divisional application in accordance with the search report.

Decision:

Article 1

SEGERS & BALCAEN NV, Affligemsestraat 500, 1770 LIEDEKERKE Belgium;

represented by

BRANTS Johan Philippe Emile, Pauline Van Pottelsberghelaan 24, 9051, GHENT;

CRABBE Ellen, Pauline van Pottelsberghelaan 24, 9051, GHENT;

a Belgian invention patent with a term of 20 years, subject to payment of the annual fees as referred to in Article XI.48, § 1 of the Code of Economic Law, for: Improved multilayer shrink film and method of manufacturing it.

INVENTOR (S):

BALCAEN Paul, Afflimgemsestraat 500, 1770, LIEDERKERKE;

PRIORITY :

BREAKDOWN:

Split from basic application: Filing date of the basic application:

Article 2. - This patent is granted without prior investigation into the patentability of the invention, without warranty of the merit of the invention, nor of the accuracy of its description and at the risk of the applicant (s).

Brussels, 26/09/2018,

With special authorization:

BE2017 / 5606

IMPROVED MULTI-LAYER KRI MPFOLI E AND METHOD FOR MANUFACTURING IT

TECHNICAL DOMAIN N

The invention relates to a multilayer shrink film comprising low density polyethylene (LDPE) and an anti-static additive.

STATE OF THE TECHNI EK

LIS 4 229 241, LIS 4 898 771 and LIS 7 247 680 describe compositions and multilayer shrink films comprising low density polyethylene (LDPE) and an anti-static additive.

However, these documents do not provide for long-term anti-static properties. In particular, the anti-static effect decreases with use. These documents also do not provide measures to ensure good printability in combination with a long-lasting antistatic effect.

The present invention aims to solve at least some of the above-mentioned problems.

SUMMARY OF THE INVENTION

In a first aspect, the present invention relates to a multilayer shrink film for packaging goods, according to claim 1.

In a second aspect, the present invention relates to a method of manufacturing a multilayer shrink film, according to claim 14.

An internal anti-static additive migrates to the surface of the shrink film to reduce the electrical resistance (increase electrical conductivity). When gripping, sliding, rubbing, wetting, and the like, the anti-static effect can be reduced by removing the anti-static additive from the surface. Because the intermediate layer comprises an increased weight percentage of the antistatic additive, an antistatic additive can migrate to the surface for a longer period of time, and thus provide a long-lasting good and uniform antistatic effect there.

BE2017 / 5606

A high concentration of anti-static additive makes adhesion of ink difficult for printing the film. Due to the time-spreading concentration profile, a good replenishment of the antistatic additive on the surface is ensured, without an increased concentration being present in the outer and inner layer from the start. This allows better initial adhesion of ink.

DETAILED DESCRIPTION

The invention relates to a multilayer shrink film for packaging goods and a method for manufacturing it. The invention has been summarized in the section provided for that purpose. In what follows, the invention is described in detail, preferred embodiments are illustrated, and the invention is illustrated by examples.

Unless otherwise defined, all terms used in the description of the invention, including technical and scientific terms, have the meaning generally understood by those skilled in the art of the invention. For a better assessment of the description of the invention, the following terms are explicitly explained.

“A”, “the” and “it” refer to both singular and plural in this document unless the context clearly assumes otherwise. For example, "a segment" means one or more than a segment.

When "about" or "round" is used in this document with a measurable quantity, a parameter, a duration or moment, and the like, it means variations of +/- 20% or less, preferably +/- 10% or less, more preferably +/- 5% or less, even more preferably +/- 1% or less, and even more preferably +/- 0.1% or less than and of the quoted value, insofar as such variations of are applicable in the described invention. However, this should be understood to mean that the value of the quantity using the term "about" or "round" is itself specifically disclosed.

The terms "include", "include", "consist of", "consist of", "include", "contain", "contain", "include", "include", "contain", "contain" are synonyms and are inclusive or open terms that indicate the presence of what follows, and do not exclude or prevent the presence of other

BE2017 / 5606 components, features, elements, members, steps, known from or described in the prior art.

Quoting numerical intervals through the endpoints includes all integers, fractions, and / or real numbers between the endpoints, including these endpoints.

A non-exhaustive example list of plastics includes acrylonitrile butadiene styrene (ABS), ethylene acrylic acid (English: ethylene acrylic acid (EAA)), ethylene ethyl acrylate (EEA), ethylene methyl acrylate (EMA), ethylene vinyl acetate (EVA), ethylene vinyl alcohol (EVOH) (phenol formaldehyde) formaldehyde (PF)), glycol-modified polyethylene terephthalate (PET-G), high impact polystyrene (HIPS), high density polyethylene (HDPE), ionomers (ION), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), melamine formaldehyde (MF (PA), polybutylene (PB), polycarbonate (PC), polyepoxide (epoxy), polyester (PES), polyetheretherketone (PEEK), polyetherimide (PEI), polyethylene (PE), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyimide (PI), polylactide (English: polylactic acid (PLA)), polymethyl methacrylate (PMMA), polypropylene (PP), polystyrene (PS), polytetrafluoroethylene (PTFE), polyurethane (PU), polyvinyl acetate (PVAC), polyvinylchlori the (PVC), polyvinylidene chloride (PVDC), styrene acrylonitrile (SAN), and urea formaldehyde (UF). Although the invention focuses in the following on specific plastics and specific anti-static additives, those skilled in the art will appreciate that the present invention can also be applied to other plastics and other anti-static additives.

In a first aspect, the present invention relates to a multilayer shrink film for packaging goods. The multilayer shrink film includes an outer layer, an inner layer, and an intermediate layer positioned between the outer layer and the inner layer. Each of the outer, inner and intermediate layers includes low density polyethylene (LDPE) and the same internal anti-static additive. The weight percentage of the anti-static additive is higher in the intermediate layer than in each of the outer layer and the inner layer. Preferably, the multi-layer shrink film is a three-layer shrink film, the shrink film consisting of the outer, inner and intermediate layer.

In a preferred embodiment, the value by weight of the antistatic additive is at least 25% higher in the intermediate layer than in each of the outer and inner layers, preferably at least 30% higher in the intermediate layer than in each of the outer and inner layers, at more preferred at least 35% higher in the intermediate layer than

BE2017 / 5606 in each of the outer and inner layer, even more preferably at least 40% higher in the intermediate layer than in each of the outer and inner layer, even more preferably at least 45% higher in the intermediate layer than in each of the outer and inner layer, and most preferably at least 50% higher in the intermediate layer than in each of the outer and inner layer.

Plastics are electrically insulating. This can cause an uneven distribution of electrical charge on the surface. Furthermore, other undesired effects such as dust attraction, reduced transparency and undesired sticking of the foil can also hereby occur. One solution is to increase the electrical conductivity of the surface of the foil. This can be done by adding internal anti-static additives, applying an external anti-static coating, or adding conductive fillers. Disadvantages of an external anti-static coating are additional process steps required and high durability required. After all, once the coating is damaged or removed, the surface is no longer antistatic. Internal anti-static additives have the advantage that they migrate through the foil to the surface. A particular and common type of anti-static additive includes a hydrophobic portion and a hydrophilic portion. The hydrophobic portion is located on the surface of the film and the hydrophilic portion attracts ambient moisture to decrease the electrical surface resistance (increasing the surface conductivity). An external anti-static coating is typically applied with a density of 10 to 100 mg / m ² . Internal anti-static additives are typically added with a weight percentage of 0.05 to 8 depending on the type of plastic. Conductive fillers are typically added at a weight percentage of 5 to 30.

A non-exhaustive example list of conductive fillers includes carbon black, conductive fibers and nanomaterials. A non-exhaustive example list of internal anti-static additives includes alkyl sulfonates, diethanol amides, esters of phosphoric acid, ethoxylated amines, glycerol esters such as glycerol monostearate (GMS), long chain aliphatic amines and amides, long chain alkyl phenols, polyethylene glycol ester, polyols and quaternary ammonium salts.

The present invention is advantageous because it ensures long-term anti-static action. When gripping, sliding, rubbing, wetting, and the like, the anti-static effect can be reduced by removing the anti-static additive from the surface. Since the intermediate layer comprises an increased weight percentage of the antistatic additive, an antistatic additive can be used for a longer period of time.

BE2017 / 5606 migrate to the surface. As a result, the shrink film can provide a long-lasting and uniformly anti-static surface. The increased weight percentage in the intermediate layer spreads over time to the outer and inner layers to the surface, where the anti-static additive is removed by use and replenished by migration.

The presence of much anti-static additive is undesirable for certain process steps. Eg. for printing the film, a high concentration of anti-static additive makes ink adhesion difficult. Due to the time-spreading concentration profile, a good replenishment of the antistatic additive on the surface is ensured, without an increased concentration being present in the outer and inner layer from the start. In the example of printing this allows better initial adhesion of ink.

Not only the antistatic properties are important for a shrink film, but also the mechanical properties, such as tensile strength, elongation, tear resistance and puncture resistance, as well as shrink properties. The specific compositions, thicknesses and sequence of the different layers as well as certain process steps are important for this.

In a preferred embodiment, each of the outer, inner and intermediate layers comprises linear low density polyethylene (LLDPE). Preferably, each of the outer and inner metallocene layers comprises linear low density polyethylene (mLLDPE). In a preferred embodiment, the intermediate layer comprises high density polyethylene (HDPE). Preferably, the intermediate layer comprises a weight percentage of at least 23, preferably at least 25, more preferably at least 27, even more preferably at least 29, and most preferably at least 31 of HDPE.

In a preferred embodiment, each of the outer, inner and intermediate layers comprises the same anti-static masterbatch, the anti-static masterbatch comprising at least one of an ethoxylated amine, a diethanolamide and glycerol monostearate (GMS). Preferably, the anti-static masterbatch comprises an ethoxylated amine. Even more preferably, the anti-static masterbatch comprises an ethoxylated tertiary fatty acid amine. Ethoxylated amines have good antistatic activity and migration properties in plastics comprising LDPE, LLDPE and / or HDPE.

In a preferred embodiment, each of the outer and inner layers comprises the anti-static masterbatch in a weight percentage of at least 1.6, preferably at least 1.7,

BE2017 / 5606 more preferably at least 1.8, even more preferably at least 1.9, and most preferably at least 2.0. In this preferred embodiment, the intermediate layer comprises the anti-static masterbatch in a weight percentage of at least 2.2, preferably at least 2.4, more preferably at least 2.6, even more preferably at least

2.8, and most preferably at least 3.0.

The multilayer shrink film comprises a film thickness. Each of the outer and inner layers includes a layer thickness. The intermediate layer includes an intermediate thickness. In a preferred embodiment, the layer thickness of each of the outer and inner layers is equal to at least 5% and at most 25%, preferably at least 7.5% and at most 22.5%, more preferably at least 10% and at most 20%, and most preferably at least 12.5% and at most 17.5% of the film thickness. In a preferred embodiment, the intermediate thickness is equal to at least 50% and at most 90%, preferably at least 55% and at most 85%, more preferably at least 60% and at most 80%, and most preferably at least 65% and at most 75% of the foil thickness. In a preferred embodiment, the multilayer shrink film comprises an average film thickness of at most 75 µm, preferably at most 67.5 µm, more preferably at most 60 µm, even more preferably at most 55 µm, even more preferably at most 50 µm, and most preferably at most 45 pm.

In a preferred embodiment, each of the outer, intermediate and inner layers are transparent, and the shrink film is printed on the inner layer.

In a preferred embodiment, the multilayer shrink film comprises a weight of up to 90 g / m ^2, preferably at most 80 g / m ^2, more preferably at most 70 g / m ^2, even more preferably at most 60 g / m ^2, even more preferably at most 50 g / m ² , and most preferably at most 40 g / m ² .

In a preferred embodiment, the multilayer shrink film comprises a machine direction and a transverse direction. The multilayer shrink film includes an elongation (ASTM 882) per thickness (ISO 374) ratio in the machine direction of at least 8.75% / pm and in the transverse direction of at least 11.25% / pm. The multilayer shrink film includes a tear resistance (ASTM 1922) per thickness (ISO 374) ratio in the machine direction of at least 50 mN / pm and in the transverse direction of at least 62.5 mN / pm.

In a second aspect, the present invention relates to a method of manufacturing a multilayer shrink film according to the first aspect of the present invention. A professional with ordinary knowledge in the field will appreciate that

Preferred embodiments of the first aspect also relate to the second aspect, and preferred embodiments of the second aspect also relate to the first aspect.

The method includes the step of blowing coextruding the outer, intermediate and inner layers to form a blown bubble. The shrink film preferably comprises an inflation ratio (English: blow-up ratio) of at least 2.7. The inflation ratio is the ratio of the diameter D of the blown bubble to the diameter D _head of the extrusion _head . The higher the inflation ratio, the better the shrinkage properties of the multilayer shrink film. The method further comprises dividing, preferably cutting, the blown bubble essentially two equally wide shrink films of width b, each being wound on a roll. The widths b of the shrink films are linked to the diameter D according to 2 b = π D. With a diameter D _head of the extrusion _head the following applies: 2 b / (n D _head )> 2.7.

In what follows, the invention is described by means of a non-limiting example illustrating the invention, which is not intended or should be construed to limit the scope of the invention.

EXAMPLE

This example concerns a three-layer shrink film comprising an outer layer, an inner layer and an intermediate layer positioned between the outer and inner layers. The shrink film has an average film thickness of about 40 µm. The outer layer comprises an average outer layer thickness of about 15% of the average foil thickness, i.e. an average outer layer thickness of about 6 µm. The inner layer comprises an average inner layer thickness of about 15% of the average film thickness, i.e. an average inner layer thickness of about 6 µm. The intermediate layer comprises an average intermediate thickness of about 70% of the average foil thickness, i.e. an intermediate thickness of about 28 µm.

The outer layer and the inner layer comprise an essentially equal composition comprising:

• approximately 2% by weight of anti-static masterbatch;

• about 10 weight percent of low density polyethylene (LDPE); and • about 88 weight percent of metallocene-based LLDPE (mLLDPE).

The antistatic masterbatch is suitable for LDPE, HDPE and LLDPE, and has a density (ISO 1183) of about 0.940 g / cm ^3, a bulk density of about 550 ^{θ ΒΕ2017} / 5606 kg / m ^3; and a moisture content of less than 1500 ppm. The metallocene-based LLDPE includes hexene as a comonomer and with a density (ISO 1183) of about 0.927 g / cm ³ , a melt flow rate (190 ° C / 2.16 kg, ISO 1133) of about 1.2 g / 10 min, a melt temperature ( ISO 11357) of approximately 119 ° C and a Vicat temperature (ISO 306) of approximately 118 ° C. The metallocene-based LLDPE includes antioxidant additives and polymer process additives (PPA), as well as about 750 ppm of anti-blocking agents and about 1250 ppm of slip agents.

The intermediate layer includes:

About 3% by weight of the same anti-static masterbatch;

• about 20 weight percent high density polyethylene (HDPE);

About 32 weight percent of low density polyethylene (LDPE); and • about 45 weight percent of metallocene-based LLDPE (mLLDPE).

The metallocene-based LLDPE has a density (ISO 1183) of about 0.932 15 g / cm ³ , a melt flow rate (190 ° C / 2.16 kg, ISO 1133) of about 0.5 g / 10 min, a melt temperature (ISO 11357) of about 123 ° C and a Vicat temperature (ISO 306) of approximately 115 ° C. It is suitable for blends comprising LDPE and / or LLDPE. It includes antioxidant additives as well as polymer process additives (PPA).

The three-layer shrink film is transparent and includes the properties listed in Table 1.

MR stands for machine direction and DR for cross direction.

Table 1 - Properties of the three-layer shrink film

Property Value Unit Norm Min. thickness 36 p.m ISO 374 Gern. thickness 40 p.m ISO 374 Max. thickness 44 p.m ISO 374 Tensile strength MR 17.5 N / 1 5 mm ASTM 882 Tensile strength DR 12.5 N / 1 5 mm ASTM 882 Stretch MR 350 % ASTM 882 Rack DR 450 % ASTM 882 Tear resistance MR 2000 mN ASTM 1922 Tear resistance DR 2500 mN ASTM 1922 Puncture resistance (dart drop) 60 g ASTM 1709 Weight 37.1 ± 2 g / m ²

BE2017 / 5606

Claims (14)

CONCLUSI ES Multilayer shrink wrap for packaging goods, comprising an outer layer, an inner layer and an intermediate layer positioned between the outer layer and the inner layer, each of the outer, inner and intermediate layers comprising low density polyethylene and the same antistatic masterbatch comprising at least one of an ethoxylated amine, a diethanolamide and glycerol monostearate, characterized in that the weight percentage of the antistatic masterbatch is at least 25% higher in the intermediate layer than in each of the outer and inner layers. Multilayer shrink film according to any one of the preceding claims, wherein the anti-static masterbatch comprises an ethoxylated amine. The multilayer shrink film according to the preceding claim 2, wherein each of the outer and inner layers comprises the anti-static masterbatch in a weight percentage of at least 1.6. Multilayer shrink film according to any of the preceding claims, wherein each of the outer, inner and intermediate layers comprises linear low density polyethylene. The multilayer shrink film according to the preceding claim 4, wherein each of the outer and inner metallocene layers comprises linear low density polyethylene. Multilayer shrink film according to any one of the preceding claims, wherein the intermediate layer comprises high-density polyethylene in a weight percentage of at least 23. Multilayer shrink film according to any one of the preceding claims, wherein the multilayer shrink film is a three-layer shrink film, consisting of the outer, inner and intermediate layer. Multilayer shrink film according to any of the preceding claims, wherein the multilayer shrink film comprises a film thickness, each of the outer and inner layers comprising a layer thickness of at least 5% and at most 25% of the film thickness. Multilayer shrink film according to any one of the preceding claims, wherein the multilayer shrink film comprises a film thickness, the intermediate layer comprising an intermediate thickness of at least 50% and at most 90% of the film thickness. BE2017 / 5606 Multilayer shrink film according to any of the preceding claims, wherein the multilayer shrink film comprises an average film thickness of at most 75 µm. Multilayer shrink film according to any one of the preceding claims, wherein the multilayer shrink film is produced by blow co-extrusion of the outer, intermediate and inner layer. The multilayer shrink film according to the preceding claim 11, wherein the multilayer shrink film has an inflation ratio of at least 2.7. Multilayer shrink film according to any one of the preceding claims, wherein the outer, intermediate and inner layer are transparent, preferably the shrink film printed on the inner layer. 14. Method for manufacturing a multilayer shrink film according to any of the preceding claims, comprising the step of blowing coextruding the outer, intermediate and inner layer. BE2017 / 5606 IMPROVED MULTI-LAYER KRI MPFOLI E AND METHOD FOR MANUFACTURING IT