JPS6134984B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a polyolefin laminate having good heat resistance, abrasion resistance, stress cracking resistance, etc. Conventionally, polyolefins such as high-density polyethylene, polypropylene, and low-density polyethylene have been widely used as materials for containers for detergents and chemicals, pipes for central heating or transporting chemicals, and for covering electric wires. However, these products made from polyolefin must be used under certain restrictions due to the material properties of uncrosslinked polyolefin itself. For example, detergent bottles, central heating pipes, ski lining materials, and the like made of high-density polyethylene are restricted from being used in harsh environments due to environmental stress cracking, heat resistance, and abrasion resistance. Further, although low density polyethylene is used as a wire coating, the reality is that further improvements are desired in terms of heat resistance and stress cracking resistance. As a means to address these problems, a method of using a crosslinked polyolefin with excellent material properties in place of the above-mentioned uncrosslinked polyolefin can be considered. However, when crosslinked polyolefin is used alone, it is more expensive than when uncrosslinked polyolefin is used, and impact resistance and anti-extension properties are lowered, leaving problems in terms of practicality. Therefore, the present inventors have attempted to cover the disadvantages of uncrosslinked polyolefin with crosslinked polyolefin by layering crosslinked polyolefin on polyolefin that will not be crosslinked in the future (hereinafter referred to as uncrosslinked polyolefin), and at the same time to create an economical solution. I thought of solving the above problem as well. However, it has been found that implementing this new method requires solving another problem: poor adhesion of both uncrosslinked and crosslinked polyolefin layers. For example, even if crosslinked polyolefin and uncrosslinked polyolefin are press-laminated at a temperature higher than the melting point of polyethylene, the adhesion between the two layers is poor and it is not practical. In consideration of the problem of adhesion in the case of this laminate, and another requirement of ease of manufacture, the present inventors have developed a laminate with good heat resistance, abrasion resistance, stress cracking resistance, etc. In order to produce a polyolefin laminate having an uncrosslinked polyolefin layer and a crosslinked polyolefin layer at a relatively low cost, a crosslinked silane-modified polyolefin was selected as the crosslinked polyolefin. This is because the silane-modified polyolefin reacts with moisture in the presence of the silanol condensation catalyst and is easily crosslinked. In addition, regarding the problem of adhesion between the silane-modified polyolefin layer containing the silanol condensation catalyst and the uncrosslinked polyolefin layer, it is still sufficient to blend the silane-modified polyolefin with the silanol condensation catalyst and melt it before molding. Since they are not cross-linked (because the gel fraction is low), both layers are firmly melted and bonded, and then the silane-modified polyolefin layer side containing at least a silanol condensation catalyst of the laminate is brought into contact with moisture to form the silane-modified polyolefin layer. By a method of crosslinking, or after melting and laminating unmodified polyolefin and vinyl silane modified polyolefin, applying a silanol condensation catalyst to the surface of the vinyl silane modified polyolefin layer,
The problem was then solved by bringing water into contact with this surface. Therefore, the laminate obtained by the present invention has a structure in which an uncrosslinked polyolefin layer and a crosslinked silane-modified polyolefin layer are firmly adhered to each other. In the present invention, the silane-modified polyolefin layer has the general formula R—Si(OR') ₃ [where R is H ₂ C=
CH—or R′ is CH ₃ —, C ₂ H ₅ —, CH ₃ —O—CH ₂ —CH ₂ — or

Represents a group of [Formula]. It can be obtained by melt-kneading the vinyl silane shown in ] and polyolefin in the presence of a radical-generating catalyst. Examples of the vinylsilane represented by the above formula include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, and vinyltriacetoxysilane. In addition, examples of radical-generating catalysts include dicumyl peroxide, benzoyl peroxide, 2,5-
Dimethyl-2,5-di(tert-butylperoxy)
Organic peroxides such as hexyne-3,3,5,5-trimethylhexanoyl peroxide, 2,5-dimethylhexane-2,5-dihydroperoxide, or azoisobutyronitrile, dimethylazoisobutyrate, etc. The following azo compounds are mentioned. Examples of polyolefins include homopolymers such as high-density polyethylene, polypropylene, density polyethylene, and polybutene-1, ethylene copolymers such as ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, and ethylene-methyl acrylate copolymers. Further examples include propylene copolymers such as propylene-ethylene copolymers and propylene-butene-1 copolymers. In order to produce silane-modified polyolefin using these materials, first the polyolefin is
To 100 parts by weight, 0.001 to 5 parts by weight of vinylsilane and 0.01 to 1 part by weight of a radical-generating catalyst are blended, and then this mixture is melt-kneaded at a reaction temperature of 150 to 280°C. For melt-kneading, a normal melt-kneader such as a Banbury mixer, roll mill, or extruder can be used, but an extruder is preferable from the viewpoint of productivity. Next, as the silanol condensation catalyst added to the silane-modified polyolefin obtained by the above method, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctate, monoacetic acid
Examples include dioctyltin compounds such as tin and lead naphthenate, amines such as ethylamine, dibutylamine, and hexylamine, and organic acids such as capric acid and stearic acid. In this case, the silanol condensation catalyst is used per 100 parts by weight of the silane-modified polyolefin.
It is used in a proportion of 0.01 to 5 parts by weight. Methods for mixing silane-modified polyolefin and silanol condensation catalyst include preparing silane-modified polyolefin in advance, mixing it with silanol condensation catalyst, and extruding it; A method of mixing a catalyst and extruding it can also be used. Furthermore, a method of applying a silanol condensation catalyst to the surface of a silane-modified polyolefin layer that does not contain a silanol condensation catalyst can also be used. On the other hand, as the uncrosslinked polyolefin constituting the other layer laminated on the layer containing the silane-modified polyolefin and silanol condensation catalyst described above, the aforementioned polyolefin before silane modification can be used. These polyolefins may be used alone or in combination. Further, the uncrosslinked polyolefin and the backbone polyolefin of the silane-modified polyolefin may be the same or different. Now, as a method of melt-laminating a silane-modified polyolefin containing a silanol condensation catalyst and an uncrosslinked polyolefin, which is one of the key points of the present invention, each is supplied using separate extruders, and coextruded using the same die. One method is the double injection method, in which one resin is injected into a mold in advance, and the other resin is injected into the mold. Sheets of each resin are prepared in advance, and these are stacked together. A method of melting and laminating by heating and pressurizing with a press molding machine, etc. can be used. The molding temperature in these is preferably 150 to 280°C. In any case, in the lamination stage, the silane-modified polyolefin layer must be uncrosslinked or the degree of crosslinking must be at a gel fraction of 35.
It is important that the thickness be as low as % by weight or less, and as long as this is satisfied, other lamination methods can also be used. In the thus obtained laminate, the crosslinkable silane-modified polyolefin layer is then crosslinked with water. In this case, crosslinking methods include leaving the laminate in the atmosphere for a long period of time and allowing it to react with moisture in the atmosphere, immersing the laminate in hot water or water, or exposing the laminate to steam. In short, a method of bringing moisture into contact with silane-modified polyolefin can be used. The degree of crosslinking (gel fraction) of the crosslinked vinylsilane-modified polyolefin thus obtained is 55% or more, preferably 65% or more. In addition, as for the laminated structure, in addition to the two-layer structure of an uncrosslinked polyolefin layer and a crosslinked silane-modified polyolefin layer, the intermediate layer is an uncrosslinked polyolefin layer, and the front and back layers are composed of a crosslinked silane-modified polyolefin layer. It is also possible to have a layered structure or the opposite structure, or even a five-layered structure of crosslinked silane-modified polyolefin/uncrosslinked polyolefin/crosslinked silane-modified polyolefin/uncrosslinked polyolefin/crosslinked silane-modified polyolefin. Furthermore, in order to impart gas barrier properties to the laminate, the surface of the crosslinked silane-modified polyolefin layer was coated with nylon 6,6, nylon 10, nylon 6,
10, a gas barrier resin selected from polyamide resins such as nylon 6, thermoplastic polyester resins such as polyethylene terephthalate and polybutylene terephthalate, and saponified products of ethylene-vinyl acetate copolymers may be further laminated. In order to reduce the cost of the product, it is preferable to make the uncrosslinked polyolefin layer thicker than the other resin layers. The laminate according to the present invention can be widely used as packaging materials such as containers for detergents and medicines, pipes, wire coating materials, trays for frozen foods, retort pouches, and bag-in pouches. Examples of the present invention will be described below, from which the effects of the present invention will become clearer. The measurement results for peel strength and stress cracking resistance (ESC resistance) for each example are as follows:
Table 1 together with the measurement results for those comparative examples
and shown in Table 2. <Example 1, Comparative Example 1> Density 0.95g/cc, melt index 0.5g/10
After mixing 100 parts by weight of high-density polyethylene [Yukalon Hard BX-50 (trade name) manufactured by Mitsubishi Yuka Co., Ltd.], 2 parts by weight of vinyltrimethoxysilane dissolved in acetone, and 0.2 parts by weight of dicumyl peroxide, the mixture was mixed. were melt-kneaded at 230°C using an extruder with a diameter of 65 mm and a L/D of 24, extruded into strands, cooled and cut, and pellets of modified polyethylene to which 1.5% by weight of vinylsilane was added (gel fraction 0%) was obtained. Next, 100 parts by weight of the pellets were mixed with 5 parts by weight of BX50 containing 2% by weight of dibutyltin laurate, and then mixed into one extruder.
50 is fed to other extruders, each melt-kneaded at 230°C and fed into one common die, and then co-extruded to form a laminated parison and blow-molded into a bottle shape (at this point gel fraction of the inner layer at 20%). Then, heat the resulting bottle at 120℃.
The average wall thickness of the inner layer of crosslinked polyethylene (gel fraction 75%) is 100% by blowing steam into it to cause crosslinking.
μ, that of the outer layer of uncrosslinked polyethylene is 900μ
A hollow bottle with a capacity of 700ml was obtained. For comparison, the wall thickness is 1mm formed using only BX-50.
The hollow bottle was designated as Comparative Example 1. <Example 2, Comparative Example 2> Low-density polyethylene with a melt index of 4 g/10 minutes and a specific gravity of 0.918 [Yukalon LK30 manufactured by Mitsubishi Yuka Co., Ltd.
(Product name)] To 200 parts by weight, 4 parts by weight of 3,5,5-trimethylhexanoyl peroxide and 6 parts by weight of vinyltris(β-methoxyethoxy)silane were added, and the mixture was heated to 200°C with a diameter of 40 mm.
Vinyl silane is passed through an extruder of L/D28.
A modified polyethylene containing 1.7% by weight was obtained. Next, 2% by weight of dibutyltin laurate was added to 100 parts by weight of this modified polyethylene.
5 parts by weight of LK30 was added to one extruder, and a melt index was added to another extruder.
Ethylene-vinyl acetate copolymer with a vinyl acetate content of 12% by weight was supplied at 5.5 g/10 minutes, and each
The mixture was melt-kneaded at 200°C, supplied to one inflation die, and then coextruded to obtain a laminated film (thickness of each layer: 20μ, 20μ). Note that cooling in this case was performed by immersing the film in water. Also, Comparative Example 2 for this Example 2
A laminated film of LK30 and copolymer was used.

[Table] <Example 3, Comparative Example 3> High density polyethylene (melt index
0.1, density 0.955) [Mitsubishi Yuka Yucalon Hard
BX70 (trade name)] A mixture of 100 parts by weight of vinyltrimethoxysilane, 2 parts by weight of vinyltrimethoxysilane, and 0.02 parts of dicumyl peroxide was passed through an extruder of L/D20 set at a temperature of 230°C to obtain silane-modified polyethylene. Next, this modified polyethylene was heated to 180℃ to a thickness of 1
It was formed into a press sheet of mm. BX70 was also molded into a press sheet with a wall thickness of 1 mm under the same conditions. These two pressed sheets were superimposed and molded again at a temperature of 180°C to obtain a laminated sheet with a wall thickness of 1.95 mm. A toluene solution of dibutistin dilaurate was applied to the surface of this laminated sheet, and then crosslinked by immersing it in 100°C warm water. The gel fraction of the modified polyethylene layer was 70%. This laminated sheet is 20mm x 100
The 10 mm width at both ends of the sheet-like specimen obtained by punching it into a mm shape was fixed with a jig, and the specimen was placed in an oven at 140°C. At this time, the amount of deformation (strain amount) of the central portion over time was measured. As Comparative Example 3, a 1.95 mm press sheet of BX70 was also evaluated under the same conditions. The results are shown in Table 2 below.

[Table] As is clear from this example, the heat resistance of the example was greatly improved. <Example 4, Comparative Example 4> Two sheets of cross-linked high-density polyethylene with a gel fraction of 80% and non-cross-linked high-density polyethylene (BX50) each having a wall thickness of 1 mm were molded using a press molding machine.
When laminated at 160° C. and cooled, the adhesive strength between both layers was measured and found to be 40 Kg/cm ² . Further, the weight of the modified polyethylene before crosslinking used in Example 3 and BX50 was 250 kg/cm ² . <Examples 5, 6 and 7> Instead of vinyltrimethoxysilane in Example 1, vinyltriacetoxysilane (Example 5), γ-methacryloxypropyltrimethoxysilane (Example 6), γ-methacryloxypropyltris Two-layer hollow bottles were obtained in the same manner as in Example 1, except that (methoxyethoxy)silane (Example 7) was used, and these were evaluated. The results are shown in Table 3. Regarding the hollow bottle of Example 5, the gel fraction of the modified polyethylene layer immediately after molding was measured and found to be 18%.

[Table] (Measurement method) Peel strength: Peel tear strength, tensile speed 100mm/
ESC resistance: Put 70 c.c. of Lypon F undiluted solution (Lion Oil surfactant) into a bottle, weld a polyethylene sheet to the mouth of the bottle and seal it completely, then put it in an oven at 70℃ and stress-freeze it. Measure the time it takes for the tsukku to occur. Heat resistance deformation temperature: Temperature at which a hollow bottle deforms Gel fraction: Weight percentage of insoluble content of resin when Soxhlet extraction is performed with boiling xylene for 10 hours.

Claims (1)

[Claims] 1. General formula R--Si which can be crosslinked with water in the presence of a layer made of polyolefin and a silanol condensation catalyst
(OR') ₃ [Here, R is H ₂ C=CH- or R′ represents CH ₃ —, C ₂ H ₅ —, CH ₃ —O—CH ₂ —CH ₂ — or a group of [Formula]. ] is laminated while both are in a molten state, and then the latter layer is crosslinked by bringing the resulting laminate into contact with water. A method for producing a characteristic polyolefin laminate.