JPS6348894B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyolefin compositions suitable for adhesive layers in laminates. Conventionally, by laminating polyolefin with metal foil or other synthetic resin layers, moisture-proof, oil-proof,
Laminated films and containers with improved abrasion resistance, heat sealability, mechanical strength, etc. are known. However, polyolefins have poor affinity with metal foils and other synthetic resins and cannot be bonded by normal molding methods, so for example, natural or synthetic inorganic compounds such as talc, etc. It is known to add small amounts of zeolite, diatomaceous earth, bentonite, etc. Among these inorganic compounds, bentonite whose main component is montmorillonite is excellent in improving adhesive properties. However, bentonite has a high ability to adsorb moisture, and polyolefin compositions to which simply dried bentonite is added will adsorb moisture in the atmosphere before molding, so they will foam during extrusion molding at high temperatures, such as extrusion coating. In addition, there was a drawback that adhesive strength decreased due to foaming. The present invention was made for the purpose of improving these drawbacks of conventionally known polyolefin compositions containing bentonite. For 100 parts by weight of polyolefin modified with saturated carboxylic acid or its derivative,
The molar ratio of silica and alumina is 9 or more, the water adsorption capacity is 2% by weight or less, and the specific surface area is 150m ² /g.
0.02 to 2 parts by weight of the above bentonite treated product is blended. The polyolefins used as raw materials for the modified polyolefin in the present invention include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1
- A homopolymer of α-olefin such as butene, 1-hexene, 4-methyl-1-pentene or a copolymer of one of the above monomers with up to 10 mol%, preferably up to 7 mol% of other α-olefin. Polymers with a degree of crystallinity of 20% or more as determined by X-ray analysis. In addition, ethylene-vinyl acetate copolymers, hydrocarbon elastomers, such as ethylene-vinyl acetate copolymers,
Propylene rubber, ethylene-1-butene rubber, polyisobutylene rubber, butyl rubber, ethylene-propylene-diene terpolymer, butadiene rubber, ethylene-butadiene rubber, ethylene-butadiene rubber, isoprene rubber, and the like can also be used. Among these polyolefins, low
Preferred are medium- and high-density polyethylene, linear low-density polyethylene, polypropylene, propylene-ethylene copolymer, ethylene-vinyl acetate copolymer, ethylene-propylene rubber, ethylene-1-butene rubber, and the like. In addition, the above polyolefin is
They can be used alone or in combination of two or more. Furthermore, modified polyolefins are produced by graft-modifying part or all of the above polyolefins with unsaturated carboxylic acids or derivatives thereof. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and endo-bicyclo[2.
2.1]-5-heptene-2,3-dicarboxylic acid,
Endo-bicyclo[2・2・1]-1,4,5,
6,7,7-hexachloro-5-heptene-2,
3-dicarboxylic acid, dis-4-cyclohexene,
Examples include 1,2-dicarboxylic acid. Also,
Derivatives of unsaturated carboxylic acids include acid anhydrides,
Examples include esters, amides, imides, halides, and metal salts. Among these, maleic anhydride, acrylic acid, endo-bicyclo [2.2.
1]-5-heptene-2,3-dicarboxylic anhydride and the like are particularly preferably used. Various known methods can be used to modify the polyolefin with the above-mentioned unsaturated carboxylic acid or its derivative. For example, it is carried out by heating the polyolefin and the grafting monomer to a high temperature in the presence or absence of a solvent, with or without the addition of a radical generator. Other vinyl monomers such as styrene and vinylsilane may be present during the reaction. The amount of acid added to polyolefin is 0.001 to 2% by weight, especially
It is preferably adjusted to a range of 0.04 to 0.6% by weight.
There is no problem even if the polyolefin is partially or completely modified with an unsaturated carboxylic acid or its derivative, but from an industrial production point of view, a modified polyolefin with an addition amount of 0.01 to 3% by weight is produced in advance, and then It is preferable to mix this modified polyolefin with the unmodified polyolefin because the concentration of the amount of acid added in the composition can be adjusted appropriately. The processed product of bentonite used in the composition of the present invention uses bentonite as a starting material, which is treated with an acid to exchange a part of the metals contained therein, such as alkali metals and alkaline earth metals, with H ⁺ , and alumina Extract a part of the silica to make the silicic acid part amorphous,
The silicic acid part is converted to cristobalite by washing with water and firing, and has a moisture adsorption capacity of 2% by weight.
The following is preferably 1% by weight or less,
It is preferable that the specific surface area measured by the BET method is 150 m ² /g or more, and the molar ratio of silica to alumina, SiO ₂ /Al ₂ O ₃ , is 9 or more, particularly 10 or more. Here, the moisture adsorption capacity is determined by soaking the treated bentonite at a temperature of 700℃ for 1 hour.
After drying, quickly return to constant temperature and humidity conditions [23℃,
relative humidity (RH) of 60%], and the average value of the weight increase % was determined. If this value exceeds 2% by weight, foaming will occur and the peel strength will decrease, which is not preferable. The average particle diameter of the bentonite treated product is
It is preferably 10μ or less, particularly 2μ or less. The amount of the bentonite-treated product to be added is 0.02 to 2.0 parts by weight, preferably 0.1 to 1.5 parts by weight, based on 100 parts by weight of the polyolefin partially or completely modified with an unsaturated carboxylic acid. If the amount of the bentonite treated product added is less than 0.02 parts by weight, the adhesion will not be improved, while if it exceeds 2.0 parts by weight, the adhesion will deteriorate, which is not preferable. The modified polyolefin composition of the present invention can be prepared by various known methods. For example, after mixing each component in advance with a Henschel mixer, ribbon blender, tumbler, etc.
Examples of methods include kneading at a temperature higher than the melting point of the resin using an extractor, Banbury mixer, kneader, etc.
At this time, antioxidants, neutralizers, ultraviolet absorbers, antistatic agents, lubricants, pigments, etc. can be added as necessary. The composition of the present invention does not foam even during high-temperature extrusion molding, improves adhesion between laminates, and can provide stable adhesive strength even during long-term storage of laminates. Further, the composition does not foam due to water absorption even when extruded at high temperature after long-term storage. It is particularly useful for extrusion coating as an adhesive between an aluminum foil and a polyolefin layer of a composite film for retort food packaging. Hereinafter, the modified polyolefin composition of the present invention will be explained in detail using Examples. In addition, parts and % in Examples indicate weight, and the test method is as follows. Peel strength The laminate was cut into strips with a width of 15 mm, and the test pieces were heated and pressed (temperature 160℃, pressure 2Kg/cm ² , 2 seconds).
After that, the aluminum and adhesive layer were peeled off from one end, and a 180° peel test was conducted at a speed of 300 mm/min to use as a gripping margin. Example 1 Propylene-ethylene random copolymer (ethylene content 2.8%, melt flow index 15)
g/10 min) 54 parts, modified propylene-ethylene random copolymer with 0.3% maleic anhydride addition (ethylene content 4%, melt flow index
100g/10 minutes) 30 parts, low density polyethylene (density
0.918g/cc), melt index 7.0g/10min)
8 parts of ethylene-propylene rubber with 7.0% maleic anhydride (ethylene content 80%, melt index 7.5 g/10 min), 0.05 part of phenolic antioxidant and 0.06 part of magnesium hydroxide.
For 100 parts by weight of the base resin composition consisting of
Table 1 shows bentonite-treated product A powder (average particle size 0.8 μ) with an average moisture content of 0.8% at 23°C and RH 60%, a specific surface area of 165 m ² /g, and SiO ₂ /Al ₂ O ₃ = 10.9. After adding and pre-mixing the parts shown in 1, the mixture was pelletized using an extruder at a resin temperature of 230°C. For comparison, the average moisture value at 23°C and 60% RH is 4%, the specific surface area is 120 m ² /g, and SiO ₂ /
Bentonite treated product B with Al ₂ O ₃ = 8.1, normal bentonite [Kuribond (trade name) manufactured by Crimine Kogyo Co., Ltd. Water absorption amount measured in the same manner as Example 1 with the water adsorption amount balanced at 10%, specific surface area = 100 m ² /g,
SiO ₂ /Al ₂ O ₃ = 7.6], this bentonite was heated at 700℃,
dried for 1 hour (water absorption 10%), silica [Thyroid 244 (trade name) manufactured by Tomito Davison Chemical, water absorption 4%] and zeolite [manufactured by Nihon Kagaku Kogyo Co., Ltd.]
CS-100 (trade name), water absorption 20.1%] 0.6 parts each were added and pelletized in the same manner. After 7 days, each pellet obtained above was formed into a film with a thickness of 12 μm using an extruder at a resin temperature of 280°C.
Polyethylene terephthalate (PETP) and thickness
Using a composite film made of 9μ aluminum foil (Al) and a 50μ thick unstretched polypropylene film (CPP), the processing speed was 170 m/min.
Extrusion coating laminate is performed with a coating thickness of 9μ, and the composition is PETP/Al/extrusion coating layer/
A composite film of CPP was obtained. These composite films were measured for peel strength against Al and observed for the presence or absence of foaming, and the results are shown in Table 1.

[Table] Example 2 To see the effect during storage, the pellets from Experiment No. 2 were left indoors, and after one month and two months, composite films were formed using the pellets in the same manner as in Example 1. The peel strength against Al was measured and the presence or absence of foaming was observed, and the results are shown in Table 2.

【table】

Claims (1)

[Claims] 1. For 100 parts by weight of polyolefin in which part or all of the polyolefin is modified with an unsaturated carboxylic acid or a derivative thereof, the molar ratio of silica and alumina is 9 or more and the water adsorption capacity is 2% by weight or less,
A polyolefin composition comprising 0.02 parts by weight to 2 parts by weight of a treated bentonite having a specific surface area of 150 m ² /g or more.