FI66626C - KOMBINATIONSFILM SOM INNEHAOLLER POLYOLEFIN I VILKEN MINST ETTPOLYOLEFINSKIKT HAR GOD FOERMAOGA TILL FASTHAEFTNING VID LPOMERER SOM INNEHAOLLER POLAERA GRUPPER - Google Patents

Description

'66626

Polyolefin-containing composite film in which at least one polyolefin layer has good adhesion to polymers containing polar groups

Combinations film made of polyolefins, of which one million and polyolefins are used in the manufacture of a polymer made of polyolefins

The invention relates to a polyolefin-containing composite film in which at least one polyolefin layer has good adhesion to polymers containing polar groups.

5 Known disadvantages of polyolefins such as polyethylene and polypropylene include their poor adhesion to metals and other polar polymers. Efforts have been made to improve adhesion by a variety of methods. Examples are the surface treatment of polyolefins with acids, flame or corona discharge or using adhesives such as ethylene acrylic acid copolymers of polyolefin and the like. between the substrate. The adhesion of polyolefins to polar polymers has also been improved by blending polymers with good adhesion or copolymerization of polyethylene with monomers containing functional groups.

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Adhesion-enhancing functional groups can also be obtained by grafting various unsaturated polar compounds into the polyolefin chains, such as acrylic acid, methacrylic acid and their derivatives (such as salts), and maleic anhydride.

20

In particular, the packaging of foodstuffs in plastic films now places very high demands on packaging products. Films for food packaging may therefore contain a large number of separate layers, each chosen to give the products a certain property, for example tightness against various gases and water vapor, permeability of certain gases, sealability, etc. Often a certain layer is only necessary due to poor adhesion. such as, for example, polyolefin layers, would be adhered to other layers containing polar polymers.

The methods used to improve the adhesion of polyolefin films 5 have many disadvantages. Thus, for example, grafting maleic anhydride or acrylic acid to a polyolefin is questionable for food applications, as said substances can be considered toxic. Furthermore, for example, the addition of maleic anhydride to films is extruded before use and requires the use of solvents.

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The present invention relates to a composite film in which at least one polyolefin layer has good adhesion to polymers containing polar groups. The invention further relates to a composite film product in which the adhesive layer does not contain substances harmful to health and is easy to manufacture. The invention further relates to a composite film in which the properties of the adhesive layer can be easily adjusted during the processing process.

The polyolefin-containing composite film according to the invention, in which at least one polyolefin layer has good adhesion to polymers containing polar groups, is characterized in that said layer consists of a polyolefin modified a) by mixing 0.1-10% of unsaturated alkoxysilane and 0, 01-0.5% of a radical former under conditions such that no grafting of the silane occurs, and then b) grafted to form the final composite film.

The silane to be grafted onto the polyolefin can be any unsaturated alkoxysilane suitable for any purpose. These include e.g. vinyl-trimethoxysilane, vinyltriethoxysilane, vinyl-tris (betamethoxyethoxy) silane or gamma-methacryloxypropyltrimethoxysilane.

Grafting of polyolefins with slanes is not new per se. Initially, hydrolyzable alkoxysilanes were developed to improve the miscibility of polymers and inorganic fillers (coupling agents). In this case, the alkoxy groups of the silane are hydrolyzed to hydroxy groups, followed by condensation with the hydroxyl groups on the surface of the fillers 3,66626. In addition to alkoxy groups, these silanes have one or more groups whose chemical composition is such that it mixes well with the polymer.

5 As the alkoxy groups of silanes condense under the influence of water (and a catalyst, for example dibutyltin dellaurate), silanes have also been used in crosslinking techniques. This is based on the fact that the unsaturated alkoxysilane is grafted onto the polymer by means of peroxide and the crosslinking takes place only after the final product has been used with the aid of water or steam. In this way, the polymer can be processed at high temperatures without the risk of crosslinking, and in addition, the crosslinking step is cheaper in terms of both energy and investment costs. When using silanes for crosslinking, a condensation catalyst must always be present. According to one method, two polymer blends (silane-grafted LDPE and catalyst-containing LDPE) are added to a conventional cable-making extruder, while another method adds all raw material components directly to a special-purpose cable extruder where grafting takes place. In the manufacture of cables by said methods, it has been found that some silane-grafted LDPE grades adhere well to aluminum.

However, in the above-mentioned ways, the adhesion of silane-modified polyolefins to polymers containing polar groups is poor, and thus they are not suitable for use in the composite film product of the invention. This is because the polymers modified in the above manner have been treated for too long at the refining temperature, at which point the grafting reaction is complete. According to the invention, it has been found that in the production of the silane-modified adhesive layer, the heat treatment must be minimized and the okoating must be allowed to take place only during the processing step of the product. This is a substantial difference compared to known slane grafting methods and is due to the fact that the silane-modified polyolefin according to the invention has good adhesion to polymers containing polar groups.

In the preparation of the modified polyolefin required for the composite film according to the invention, any suitable substance capable of generating radicals at the processing temperature, i.e. in the preparation of the final product-forming composite film, is used as the radical generator for grafting, but not in the preparation of the raw material mixture. Suitable radical generators are, for example, peroxy compounds such as dicumyl peroxide. A radical scavenger is required in an amount of 0.01 to 0.5% by weight of the modified polyoleflin.

The raw material mixture is formed either by preparing a mechanical mixture of polyoleflin, silane and peroxide, or by preparing a compound mass from said 10 materials by mixing molten polyolefin, silane and peroxide. In the former case, the preparation can take place even at room temperature by mixing the polyoleflin granules, liquid silane and peroxide and stirring mechanically until mixing takes place. In the latter case, care must be taken that the temperature of the mixture does not rise so high that the peroxide used begins to decompose. In practice, the mixing temperature of the compound mass must be limited to 115-170 ° C.

The adhesion of the silane-modified polyoleflin to polar polymers can be controlled by varying the amount of silane, the amount of radical former, and temperature and time in the final product manufacturing process, thereby affecting grafting of the silane. The desired degree of adhesion can thus be achieved according to the application.

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There are various possibilities for producing the composite film according to the invention. Thus, for example, a silane-modified polyolefin can be combined in a molten state with a polymer film containing polar groups. According to another alternative, both the modified polymer and the polymer containing polar groups are in the molten state, and according to the third alternative, a film made of modified polyolefin according to the invention is combined with a film of a polymer containing polar groups in the molten state. In lime cases, grafting of the silane should take place only at this stage, the temperature and decay time of which are adjusted so that the silane has time to graft. In practice, the time required to prepare the final composite product is less than 4 minutes, preferably 2-3 minutes.

5,66626

The polyolefin-containing laminate product of the invention can be used in a variety of ways in applications that require the use of polyolefins and polymers containing polar groups in the same composite film product. One way is to use a modified polyolefin layer according to the invention for coating nallon, polyester or ordinary polyolefin directly. Another alternative is to use a silane-modified polyolefin layer as an intermediate or adhesive layer when coating nylon tubes, bottles and the like. Mention may also be made of composite films of nylon and modified polyolefin, composite films of poly-10 ester and modified polyolefin, and composite films of ordinary polyolefin and modified polyolefin. In these cases, the modified polyolefin layer can be either the outer, inner or intermediate layer of the multilayer product, depending on the intended use of the product.

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The modified polyolefin used in the polyolefin-containing laminate products according to the invention can be higher or lower density polyethylene, polypropylene or also various copolymers of ethylene and propylene, e.g. with vinyl acetate or mixtures of the above.

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The invention is described in more detail in the following examples.

Example 1 25 Strips were prepared in a Brabender extruder with a screw diameter of 19 mm, a length of 20 L / D and a compression ratio of 3/1. The temperature was 130 ° C / 200 ° C and the screw speed was 20 rpm. In this case, the residence time was about 2 minutes. The polyolefin was low density polyethylene (0.922 g / cm) with a melt index of 4 g / 10 minutes. Dicumyl peroxide (DCP) was used as the radi-30 potassium modifier and vinyltrimethoxysilane (Sil-1), vinyltriethoxysilane (Sil-2), vinyltris (betamethoxyethoxy) silane (Sil-3) and gamma-methacryloxypropylmethoxysilane (Sil-3) were used as silanes.

35 mm thick plates were pressed from the strips at 140 ° C. The polyamide film and the silane-modified polyolefin sheet were then compressed. In three cases, the polyamide was replaced by a poly 6,66626 ester film (PET). In the compression, the temperature was 200 ° C and the pressure 7.8 MPa. From the plates thus prepared, five specimens with a width of 20 mm and a length of 125 mm were cut. Samples were stored for 3 days at 23 ° C and 50% relative humidity.

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The load strength describing the adhesion was measured with an In stron traction device using a tensile speed of 50 mm / million. The force required to remove the different layers was read from the plotter, from which the adhesion could be calculated in Ncm 10

The table below shows the test results for silane-modified polyolefins. The reference is unmodified polyethylene.

Poly- DCP Silane Melt- Density Adhesion (N / cm) Extrusion- 3 15 mer%% index g / cm AI PA PET temperature

g / 10 min ° C

1. LDPE 0 0 3.9 0.920 0 0 0 200 2. "0.05 2.5 Sil-1 2.5 0.924 25 10 10 200 20 3." 0.1 5.0 "1.7 0.923 33 8 20 200 4. "0.05 2.5 Sil-2 2.8 0.922 30 2 - 200 5." 0.05 2.5 Sil-3 2.6 0.923 18 9 - 200 6. "0.05 2, 5 Sil-4 3.9 0.923 0 5 - 200 7. "0.05 2.5 Sil-1 0.1 0.924 18 5 - 200 25 8." 0.05 2.5 "2.5 0.924 2 0 3 140 9. "0.05 2.5" 2.5 0.924 94 13 40 300

The above results show that the adhesion of polyoleflin to female ion and polyester can be controlled to a certain extent e.g. by varying the amount of silane and the press temperature. The unmodified polyolefin did not adhere to the polyamide and polyester films at all.

Example 2 35

Test plates were prepared and tested for adhesion according to Example 1 except that the modified polyethylene was a high density poly- <66626 ethylene and ethylene vinyl acetate copolymer (EVA) with a vinyl acetate content of 20%. When testing the adhesion of these films to nylon, the following results were obtained: 5 Poly-DCP Silanes Melt- Density Adhesion (N / cm) Pressing 3mer%% index g / cm PA temperature

g / 10 min ° C

1. HDPE 0.05 2.5 Sil-1 0.1 0.957 0 200 10 2. "0.1 5.0" 0.1 0.957 12,300 3. EVA 0.05 2.5 "0.1 0.949 34 200

The results show that HDPE requires a higher amount of peroxide and silane and a pressing temperature than LDPE to obtain good adhesion to nylon.

Example 3 The effect of delay time on the adhesion of silane-modified LDPE to an extruder was investigated. The polyethylene used was the same as in Example 1. The amount of silane used was 1.5% Sil-1 and the amount of dicumyl peroxide was 0.03%. The temperature profile of the Brabender extruder was 130 ° C / 200 ° C and by changing the screw speed, dwell times of 1 min, 25 2 min, 2.5 min, 3 min, 3.5 min, 4 min and 6 min were obtained. The figure shows that this recipe provides optimal adhesion to nylon with a delay time of 3 min.

Example 4 30

To the LDPE polyethylene of Example 1 was added 2.5% Sil-1 and 0.05% DCP as a dry blend and a 50 blown film was prepared. A 45 mm 25 L / D Bandera was used as the extruder. The initial temperature was 130 ° C and the end temperature was 200 ° C. The screw speed was 79 min * and the nozzle size was 35,150 mm / 1 mm. The blow ratio was 1.8. The following properties of the film were measured and compared with the corresponding properties of the base polymer: 8 66626

Feature LDPE LDPE

2.5% Sil-1, 0.05% DCP Turbidity% 5.6 6.2

Gloss% 11.3 12.4 5 Tensile strength KS / PS, MPa 14.1 / 12.5 16.8 / 16.7

Yield strength KS / PS, MPa 10.8 / 9.9 11.4 / 10.4

Elongation at break KS / PS,% 340/470 490/610

Drop test g / 50% sulfur 82 69

Adhesion Al / PA N / cm 0/0 13/8 10 KS = film machine direction PS = film cross direction Turbidity, ASTM D 1003 Gloss, ASTM D 523 Tensile strength, ASTM D 882 Yield strength, ASTM D 882 Elongation at break, ASTM 882 Drop test value ASTM D 1709

Claims (3)

9 66626 Pa ten 11lvat suction door t Polyolefin-containing composite film in which at least one polyolefin layer has good adhesion to polymers containing polar groups, characterized in that said layer is formed by a polyolefin modified 5 a) by mixing 0.1-10% of unsaturated alkoxylsilane and 0.01- 0.5% radical former under conditions such that no grafting of silane occurs, and then b) grafted to form the final composite film. Composite film according to Claim 1, characterized in that the silane is vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (betamethoxyethoxy) silane or gamma-methacryloxypropyltrimethoxysilane. Composite film according to Claim 1 or 2, characterized in that it contains one or more layers of polyamide, polyester, polyethylene or polypropylene and one or more layers of modified polyolefin.