FI67563C - POLYOLEFIN SOM HAR GODA VIDHAEFTNINGSEGENSKAPER - Google Patents

Description

67563

Polyolefin with good adhesion properties Polyolefin, with good adhesion to the environment

The invention relates to a modified polyolefin which has good adhesion properties to metals and to the surfaces of substances containing polar groups.

Known disadvantages of polyolefins such as polyethylene and polypropylene include their poor adhesion to metals and polar polymers. Efforts have been made to improve adhesion by a variety of methods. Examples are the treatment of the surface of polyolefins with acids, a flame or a corona discharge or the use of 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 a polymer with good adhesion or by copolymerizing polyethylene with comonomers containing functional groups.

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Adhesion-enhancing functional groups can also be provided 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.

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Finnish patent application 813385 states that also by grafting silanes with polyolefins, good adhesion to metals (such as aluminum) and polar plastics (such as polyester and polyamide) can be obtained. The silane-modified polyolefin can be prepared from high-pressure polyethylene (LDPE), low-pressure polyethylene (HDPE, LLDPE), polypropylene (PP) or copolymers thereof, and homopolymer-copolymer blends by mixing 0.01 to 10% by weight of unsaturated alkoxysilane -% of radical formers. Grafting can take place either before the processing process or during the processing process.

The silane to be grafted onto the polyolefin can be any suitable unsaturated alkoxysilane. Such are e.g. vinyltrimethoxysilane, vinyltretoxysilane, vinyltris (betamethoxyethoxy) - __ li_. . _____ ...

2,67563 silane or gamma-methacryloxypropyltrimethoxysilane. As the radical former, any substance which generates radicals at the refining temperature but not in the homogenization step of the compound preparation can be used. Such substances include e.g. peroxide compounds 5 such as dicumyl peroxide.

Hydrolysable alkoxysilanes were originally developed to improve the miscibility of polymers and inorganic fillers (coupling agents). In this case, the alkoxy groups of the silanes hydroly-10 collapse into hydroxy groups, followed by condensation with the hydroxyl groups on the surface of the fillers. In addition to alkoxy groups, there is a group (s) whose chemical composition is such that it mixes well with the polymer. Since the alkoxy groups of silanes condense under the action of water (and a catalyst, for example dibutyltin dilaurate), silanes have been used in crosslinking techniques. This idea is based on the fact that the unsaturated alkoxysilane is grafted onto the polymer by means of a peroxide and the crosslinking takes place only after the final product has been prepared by means of water or steam. In this way, the polymer can be processed at high temperatures without the risk of crosslinking, and the crosslinking step is also cheaper in terms of both energy costs and investment costs. When using silanes for crosslinking, a condensation catalyst must always be present.

According to the Dow Corning system, two polymer blends (silane-grafted LDPE and catalyst-containing LDPE) are added to a conventional cable extruder, while according to Maillefer's system, all raw material components are added directly to a specially designed cable extruder. In connection with cable manufacturing, it has been found that some grades of silane-grafted LDPE adhere to aluminum.

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However, the use of radical generators such as peroxides in grafting has some drawbacks. In addition to grafting, peroxides also cause cross-linking, causing the melt index to drop and gels to form. In membrane applications, this is very detrimental. If peroxides could be completely omitted from the poly-35 olefin formulation and still have sufficient adhesion properties to metals and polar plastics, this would be a great advantage in film applications.

3,67563

It is an object of the invention to provide a silane-containing modified polyolefin which has good adhesion properties to metals and polar plastics and in which the silane does not necessarily have to be grafted onto the polyolefin using radical generators. The modified polyolefin according to the invention is characterized in that it contains 80-99.8% of a polyolefin (LDPE, LLDPE, HDPE, PP or copolymers or polymer mixtures thereof), 0.01-10% of an unsaturated alkoxysilane grafted onto the polyolefin itself. in a known manner by means of a free radical generator or added to a polyolefin without grafting and 0.01 to 10% carboxylic acid to improve the adhesion properties.

Grafting with silane per se improves the adhesion of polyolefin to metals and polar plastics. Even if the silane is not grafted, i.e. the peroxide is omitted, sufficient adhesion to the polyamide and polyester can be achieved. The possibility of omitting peroxide is a very great advantage in terms of the manufacturing and other properties of the final product.

The modified polyolefin according to the invention can be prepared from high-pressure polyethylene (LDPE), low-pressure polyethylene (HDPE, LLDPE), polypropylene (PP) or copolymers thereof, and mixtures of homopolymers and copolymers.

If very good adhesion is required and when the gels are not detrimental (metal coating, colored products or thick-walled products), alkoxysilanes can be grafted onto the polyolefin chain using a 0.01-0.5% by weight radical generator (such as dicumyl peroxide). Grafting can take place either before or during the breeding process. When the silane is grafted to the polyolefin chain, the alkoxysilane must have an unsaturated group. Such silanes include e.g. vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (betamethoxyethoxy) silane or gamma-methacryloxypropyltrimethoxysilane.

The long chain fatty acid can be any fatty acid having a carbon-35 hydrocarbon chain of more than five carbons. It may be saturated, unsaturated, polyunsaturated, branched or substituted. Such are e.g. myristic acid, stearic acid, behenylic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid.

/ 67563

In connection with patent application 813385, it has been stated that silane-grafted polyolefin must not be treated at excessive temperatures for too long. It has been found that the adhesion properties can be optimized for the extruder in terms of temperature and delay time. The heat treatment of the silane ok-5 doped polyolefin can be minimized by allowing the grafting to take place only at the refining stage. The radical former can be dissolved in the silane and either refined with a mixture of polyolefin, silane and radical or first prepared with a compound at such a low temperature that no grafting occurs. When the silane-grafted polyolefin contains a long chain fatty acid, the adhesion properties depend in a similar way on the temperature and lag time of the extruder.

Even in the absence of peroxide, the adhesion properties of the blends of polyolefin, silane and fatty acid depend on the temperature and lag time of the extruder. The lower the delay time, the better the adhesion-15 properties. However, when the plastic layers come together, the temperature must be as high as possible and the delay time at high temperature and high pressure as long as possible in order to obtain sufficient adhesion.

The modified polyolefin of the invention can be used in a variety of ways in applications where good adhesion to polyamide and other polar group-containing materials is required. Such uses include e.g. coating polyamide tubes and bottles directly with the modified polyolefin or using the modified polyolefin as an intermediate or adhesive layer when coating polyamide tubes, bottles and the like. Mention may also be made of the use of the modified polyolefin according to the invention as a film which adheres to the polyamide and other polar surfaces and, in addition, to the polyolefin itself. Also contemplated are coextruded multilayer films such as composite films of polyamide and modified polyolefin and composite films of polyamide, modified polyolefin and ordinary polyolefin. The modified polyolefin according to the invention can thus be applied as such or as a coating or adhesive for other films between other films, depending on the intended use.

Aluminum, steel and other metal pipes, sheet metal and other articles can also be coated with the modified polyolefin according to the invention or used as a medium. In these cases, the general

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5,67563 may be grafted onto polyolefin.

The invention is described in more detail in the examples below. Strips of silane-modified polyolefins were driven on a Brabender extruder 5 with a screw diameter of 19 mm, a length of 20 L / D and a compression ratio of 3/1. The temperature in the extruder was 120-130-140 ° C and the screw speed 30 min. In this case, the delay time was 110 s. Also the effect of temperature (120-150-170 ° C; 130-170-200 ° C) and delay time (110 s - 250 s) infection was elucidated. The polyolefins used were Leste 0y LDPE polyethylene 3 10 (melt index = 4 g / 10 min, density = 0.922 g / cm), HDPE grade HOSTALEN GD7255 manufactured by Hoechst (melt index = 5 g / 10 min, density = 0.955 3 g / cm) and the EVA grade ESC0RENE ULTRA 00220 manufactured by Esso (melt index 3 = 2 g / 10 min, density = 0.941 g / cm, vinyl acetate content = 20%). Dicumyl peroxide (DCP) was used as the radical generator and vinyltrimethoxysilane (VTMO) and vinyltris (betamethoxyethoxy) silane (VTMOEO) were used as silanes. Myristic acid, stearic acid and behenylic acid were used as long-chain fatty acids.

1 mm thick plates were pressed from the strips at 140 ° C. Thereafter, a polyamide film (PA-6), a silane-modified polyolefin sheet and an aluminum sheet were pressed together at a temperature of 210 ° C and, in the case of HDPE, also at a temperature of 250 ° C. Compression was also performed with polyester film (PET) and steel sheet at 180 ° C and 210 ° C. During compression, 90 s were preheated, the pressure was raised for 30 s and the compression pressure (20 bar) was maintained for 40 s. Five test pieces 20 mm wide and 125 mm long were cut from the samples thus prepared. Samples were stored for three days at 23 ° C and 50% relative humidity. The load strength describing the adhesion was measured with an Instron traction device 30 using a traction speed of 100 mm / min. The force required to remove the different layers could be read from the plotter, from which the adhesion could be calculated in Ncm '.

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Example I

6 67563

The effect of stearic acid on the adhesion of vinyltrimethoxysilane-grafted LDPE to polyamide was studied. 0.05% dicumyl peroxide (DCP) was used as the radical generator in the grafting.

It can be seen from Table 1 below that even small amounts of stearic acid clearly improve the adhesion to the polyamide. The infection increases as the amount of stearic acid increases to 1-2%, after which the adhesion does not improve or even decreases.

TABLE 1: Effect of stearic acid on the adhesion of vinyltrimethoxysilane (VTMO) grafted LDPE to polyamide. Dicumyl peroxide (DCP) has been used as the peroxide.

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Experiment VTMO DCP Molar ratio Stearic acid Adhesion (%) (%) DCP / VTMO (%) (N / cm) 20 1 2.5 0.02 0.005 - 5.0 2 2.5 0.02 0.005 0.05 7.8 3 2.5 0.02 0.005 0.10 8.5 4 2.5 0.02 0.005 1 12.8 5 2.5 0.02 0.005 2 11.3 25 6 2.5 0.02 0.005 3 9, 7 7 3.0 0.05 0.010 - 8.5 8 3.0 0.05 0.010 0.05 9.0 9 3.0 0.05 0.010 0.10 9.1 10 3.0 0.05 0.010 1 14.4 30 11 3.0 0.05 0.010 2 16.3 12 3.0 0.05 0.010 3 12.5

Example II 35

The effect of stearic acid on the adhesion of silane-modified polyethylene to polyamide in the case where silane has not been grafted to the polyethylene chain at all was studied. It can be seen from Table 2 below that a small amount of stearic acid improves the adhesion of vinyltrimethoxysilane-modified polyethylene to polyamide. The temperature of the extruder must be relatively low, which may be due to the VTMO evaporating at too high a temperature (boiling point 120 ° C). The delay time in the extruder must also be relatively short (2-3 minutes).

Table 2 further shows that stearic acid alone or VTMO 10 alone do not provide an improvement in adhesion to polyamide, but both components must be present (when grafting has not been used).

TABLE 2; Effect of stearic acid on the adhesion of vinyltrimethoxysilane 15 (VTMO) doped LDPE to polyamide.

Peroxide has not been used.

Experiment VTMO Extruder Delay Time Stearin Adhesion 20 (%) Final Temperature in the Extruder Acid (N / cm) (° C) (s) (%) 13 3.0 140 110 0.5 0 25 14 3.0 140 210 0.5 0 15 3.0 140 250 0.5 0 16 3.0 140 110 1.0 6.8 17 3.0 140 210 1.0 3.6 18 3.0 140 250 1.0 1.4 30 19 3, 0 170 110 1.0 0 20 3.0 200 110 1.0 0 21 - 140 110 1.0 0 22 3.0 140 110 - 0 35 8

Example III

67563

The effect of different polyolefins, silanes and long chain fatty acids on the adhesion to polyamide and aluminum was investigated.

In this case, samples were prepared in which the silane is grafted onto a polyolefin and with or without a fatty acid. In addition, there are samples to which silane and fatty acid but no peroxide have been added.

The results in Table 3 below illustrate the adhesion-improving effect of long-chain fatty acid. This is particularly evident in the case of HDPE, which, when grafted with silane, had no adhesion to polyamide or aluminum. The addition of stearic acid (1%) achieved good adhesion to the polyamide and almost as good adhesion even if the peroxide was omitted. In contrast, no improvement in adhesion to aluminum was achieved in this case.

TABLE 3: Effect of fatty acids on the adhesion of alkoxysilane-doped polyolefin to polyamide and aluminum.

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Experience Poly- Silane DCP Fatty Acid Press - Adhesion (N / cm)

sea (%) supertemperature PA AI

state (° C) 25 _ 23 LDPE 3% VTMOEO 0.05 - 210 9.6 19.2 24 LDPE 3% VTMOEO 0.05 1% Stearic acid 210 18.1 1.2 25 LDPE 3% VTMOEO - 1% Stearic acid 210 1.1 0 26 HDPE 3% VTMO 0.05 - 210/250 0/11 0/13 30 27 HDPE 3% VTMO 0.05 1% Stearic acid 210/250 30.5 / 51.3 0 / 1.1 28 HDPE 3% VTMO - 1% Stearic acid 210/250 32.1 / 52.6 0/0 29 EVA 3% VTMO 0.05 - 210 35.2 72.3 30 EVA 3% VTMO 0.05 1% Stearic acid 210 86.3 91.7 31 EVA 3% VTMO - 1% Stearic acid 210 1.0 0 35 32 LDPE 3% VTMO 0.05 1% Myristic acid 210 14.3 0 33 LDPE 3% VTMO - 1% Myristic acid 210 6.0 0 34 LDPE 37, VTMO 0.05 17, Behenic acid 210 12.6 1.7 35 LDPE 37, VTMO - 1% Behenic acid 210 0.2 0

. · ΊΛ V

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Example IV

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The example examined the adhesion values obtained by mixing LDPE, VTMO and in one case stearic acid and in one case dicumyl peroxide with a "Buss-Co-Kneader PR 46" mixer at low temperature (below 125 ° C). Each recipe was made into 20 kg. The sheets were pressed as described above at a compression temperature of 210 ° C and the adhesion to polyamide and aluminum was tested. Collapsed sandvich samples were also kept for 10 hours in boiling water, after which the adhesion was retested. The modified LDPE and polyamide were also subjected to a two-layer coextrusion by the blow film method. The final temperature of the silane-modified LDPE was 190 ° C and that of the polyamide 240 ° C and the molten polymers coalesced in the nozzle. Because silane-modified LDPE was relatively small and the coextrusion line was quite rudimentary, it was difficult to obtain uniform conditions and uniform thickness films. However, it can be seen from these films that the use of 3% VTMO and 1% stearic acid in LDPE provided such good adhesion to the polyamide layer that the layers could not be separated from each other.

20 There were also no gels in the LDPE modified in this way.

Recipes containing dicumyl peroxide, on the other hand, caused gels and the infection was weaker. The conditions under which the polymer layers coalesced (in this case, the polyamide is also in the molten state) strongly influenced the adhesion properties of the polyolefins modified with different silanes. When sandwich combinations with polyamide and aluminum were also pressed from the corresponding modified grades, similar results were obtained as before. Stearic acid improved the adhesion of VTMO-grafted polyolefin to polyamide, and less but still good adhesion was also obtained using VTMO 30 and stearic acid without peroxide. In this case, aluminum was also infected. When pressed sandvich samples were boiled for an hour in water, parallel results were also obtained, but the infection was slightly lower.

j ♦ * * f '' · 10 67563 TABLE 4; I.DPE-VTMO-stearic acid mixtures prepared by Buss-Co-Kneader PR 46 and their adhesions to polyamide and aluminum 5

Experiment VTMO DCP Stearin Adhesion (N / em) Behavioral Adhesion (%) (%) acid PA Alion order (%) in coextrusion x) x)

36 3 0.05 - 9.5 / 5.3 14.6 / 9.6 Gels III

37 3 0.05 1 13.5 / 9.0 12.2 / 11.0 Gels II

15 38 3 - 1 5.8 / 1.7 2.8 / 2.7 No gels I

No layers were removed 20 x) Boiled for 1 h in boiling water

Example 5 25

Infection was studied in the case where VDP0 and stearic acid-modified LDPE are pressed into polyester (PET) and steel. Two different temperatures (180 ° C and 210 ° C) were used for pressing. From Table 5 below, it can be seen that grafting VTMO to LDPE provided good adhesion 30 to both polyester and steel. As the pressing temperature dropped to 180 ° C, the adhesions deteriorated but were still quite good. When stearic acid was added, the adhesions to both the polyester and the steel deteriorated and when peroxide was further omitted, the deteriorations became further.

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35 11 67563 TABLE 5: Effect of stearic acid on the adhesion of vinyltrimethoxysilane (VTMO) doped or grafted LDPE to steel and polyester 5 _

Experience VTMO Molecular Ratio Stearin-Adhesion (N / cm)

(%) DCP / VTMO acid (%) PET_FE

180 ° C 210 ° C 180 ° C 210 ° C

10 39 3 0.010 - 4.2 / 10.3 9.6 / 19.2 40 3 0.010 1 0 / 4.6 0 / 1.2 41 3 1 0 / 1.7 0/0 15

Example VI

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The example studied the extrusion of VTMO and stearic acid modified EVA into polyester (PET) and steel. Two different press temperature (180 ° C and 210 ° C) were used. According to Table 6, it can be stated that grafting VTMO into EVA gives a very good adhesion to both polyester and steel. As the pressing temperature dropped to 180 ° C, the adhesions deteriorated but were still very good. When stearic acid was added to both the polyester and the steel, the adhesion weakened and when the peroxide was left out of the recipe, even lower adhesion values were obtained. With the base polymer being EVA, better adhesions were obtained for all 30 prescriptions than with LDPE.

i "τ ~ 12 67563 TABLE 6: Effect of stearic acid on the adhesion of vinyltrimethoxysilane (VTMO) doped or grafted EVA (ESCORENF. UL 00220, 20% VA) to steel and polyester 5

Experiment VTMO Molecular Ratio Stearin Adhesion (N / cm) (%) DCP / VTMO acid (%) _____PET_____________FE____

180 ° C 210 ° C 180 ° C 210 ° C

10 42 3 0.010 - 42.3 147.1 17.3 96.2 43 3 0.010 1 18.3 38.1 2.1 4.2 44 3 - 1 0 3.40 2.3 15

Example VII (comparison)

The adhesion of two commercial grades of adhesive plastic (Plexar P-1 and Surlyn A 1650) to polyamide, aluminum, polyester and steel was studied at a compression temperature of 210 ° C. It can be seen from the results in Table 7 that Plexar P-1 with their materials gives better adhesion values than Surlyn A 1650. These grades are also characterized by very good adhesion to metals, especially steel. Adhesions to polyester are again lower than to polyamide. Adhesions to polar plastics are of the order of magnitude that the same results can be obtained by modifying polyolefins with silanes and long chain fatty acids.

TABLE 7: Adhesions of competing polymer grades to polyamide, aluminum, polyester and steel.

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Experience Quality Adhesion (N / cm)

Polyamide Aluminum Polyester Steel 35 45 Plexar P-1 18.1 29.8 10.4 68.3 46 Surlyn AI650 1 1.3 1 7.3 2.3 2 3.2

Claims (3)

13,67563 PaCent claims Modified polyolefin with good adhesion properties to metals and surfaces of materials containing polar groups, characterized in that it contains 80-99.8% of polyolefin (LDPE, LLDPE, HDPE, PP or copolymers or polymer blends thereof), 0.01 -10% unsaturated alkoxysilane grafted to the polyolefin in a manner known per se by means of a free radical generator or added to the polyolefin without grafting and 0.01-10% of a long-chain fatty acid to improve the adhesion properties. Polyolefin according to Claim 1, characterized in that the long-chain fatty acid is stearic acid, myristic acid or behenyl acid. Polyolefin according to Claim 1 or 2, characterized in that the alkoxylsilane is vinyltrimethoxysilane or vinyltrls (betamethoxethoxyl) silane.