JPS5951574B2 - Adhesion method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adhering a polyolefin to a base material such as metal, nylon, or polyester through polybutadiene that has been irradiated with ultraviolet light in a molten state.

Polyolefins such as polyethylene and polypropylene are known to have extremely low adhesion to metals because they are non-polar substances and have high crystallinity. Various proposals have been made.

For example, (1) chemical treatments such as the sulfuric acid-chromate method,
Heat treatment is effective, but workability is poor because it is a wet method, and corrosion occurs in the reaction equipment because acid is used. Therefore, this method is widely used in basic research today. Industrially, (2) chemical treatment to convert unsaturated carboxylic acid into polyolefin, and further subdivided into (a) heating and dissolving polio/fin in a hydrocarbon solvent, converting unsaturated carboxylic acid into radicals. (b) A method in which a finely ground polyolefin is charged into water containing a surfactant to form a suspension, and an unsaturated carboxylic acid is grafted in the presence of a radical catalyst; (c) A method in which a polyolefin, a radical initiator, and an unsaturated carboxylic acid are preliminarily stirred in a Henschel mixer, charged into an extruder, and grafted by a mechanochemical method; (3) The surface of the polyolefin is mixed with air, oxygen, or ozone. Surface treatment method to create polar groups by oxidation, (4) flame treatment in which polyethylene is brought into direct contact with city gas or hydrocarbon gas flame, (5)
) j-discharge treatment using corona discharge, (6) surface grafting treatment in which a polar substance is grafted onto the polyolefin surface to improve adhesion; further subdivided into (a) 6 as a radiation source;
Grafting method using radiation using 0Co and monomers to be grafted such as methyl methacrylate, acrylamide, acrylic acid, methaquaryl glycidyl ether, methylol acrylamide, methyl acrylate, vinyl acetate, and (b) methyl methacrylate and maleic anhydride. (7) heat treatment in which polyethylene powder or sheet is placed on the metal surface and heated to 200 to 300°C; and (8) blending method in which inorganic filler is mixed into polyolefin. and so on. Polyolefins having good adhesive properties have been obtained by the method 5 described above or a combination thereof.

However, with these methods, in the food-related field,
It has the following drawbacks: In the chemical treatment of (1), acid, (
In the chemical treatment of 2), a reactive unsaturated carboxylic acid, a radical catalyst, and a surfactant, in the surface grafting treatment of (6), a terminally reacted monomer and a radical catalyst, and in the blending treatment of (8), an inorganic filler remains in the resin. However, it is necessary to wash the resin, and the washing process takes a long time. Also, these residues are often not removed even by prolonged cleaning. In food-related and non-food-related fields, it has the following drawbacks. (The chemical treatment (C) requires the use of a large amount of water to remove acids, etc. from the resin. Also, wastewater treatment is necessary because the wastewater contains chromium ions. (2) The chemical treatment of (2) and (b) involves the risk of fire and toxicity because it uses solvents, monomers, and radical catalysts. Therefore, adhesion may not be improved sufficiently. Treatments (3), (4), and (5) cannot provide sufficient adhesion. (6) Surface grafting treatment with radiation The irradiation equipment is expensive and dangerous.On the other hand, it is possible to improve the adhesion with polyolefin by (1) forming a thin oxide film on the metal surface, or (2) treating the metal surface with chemicals to create unevenness. Attempts have also been made to improve these methods. However, these methods of treating metal surfaces require long working hours, require treatment of wastewater containing chemicals, and have the disadvantage that chemicals may adhere to the treated metal surfaces. In order to solve these problems, the present inventors first developed a method of irradiating polyethylene and polypropylene with ultraviolet rays to improve their adhesion. Invented.
The method of irradiating polyethylene or polypropylene with ultraviolet rays is particularly effective for low-density polyethylene or high-density polyethylene, and can provide high adhesive strength. However, when polypropylene is irradiated with ultraviolet rays, a drop occurs during the irradiation. K:=The adhesive strength is lower than that of the first base. In order to solve this problem, the present inventors conducted intensive research and discovered that adhesiveness can be imparted to polyolefin and materials through polybutadiene that has been irradiated with ultraviolet rays in a heated and molten state.
In other words, it was confirmed that by imparting an adhesive group to polybutadiene through ultraviolet irradiation, it exhibited good adhesion to both the underlying base material and the polyolefin film without damaging the polyolefin film such as polypropylene. This is an invention that has been achieved.

According to the present invention, monomers such as unsaturated carboxylic acids, radical catalysts, radiation, etc. are not used, so it is advantageous in terms of hygiene and danger, and in combination with polybutadiene, which has good hygiene, it can be used directly in the food-related field. It is applicable to

The polybutadiene used in the present invention is not particularly limited and may be any type of 1,2-polybutadiene, cis-1,4-polybutadiene, or trans-1,4-polybutadiene, but 1, which is currently widely used as a food packaging material, .2-polybutadiene is practically preferred.

According to the method of the present invention, good adhesion is exhibited not only to polypropylene films but also to low density polyethylene and high density polyethylene films. Examples of specific methods of the present invention include: 1) Applying polybutadiene on a film such as metal or polyester or nylon, heating the film of polyethylene, polypropylene, etc. to the modified polybutadiene obtained by melting the polybutadiene and irradiating it with ultraviolet rays. How to crimp.

．． 2) A method in which a polybutadiene film modified by ultraviolet irradiation treatment in a molten state is prepared in advance, and the film is interposed between a metal/polyethylene, polypropylene, or polyester, nylon/PE, or PP film and bonded under heat. 3) Examples include a method in which polybutadiene and polyolefin films are laminated in this order on metal, polyester, nylon, etc., and then irradiated with ultraviolet rays when heated and melted.

5. The molten state according to the present invention is a heated state in which polybutadiene is modified by ultraviolet irradiation and exhibits a good adhesion state, and is determined by the heating temperature and heating time.

The heating temperature is at least the softening temperature of polybutadiene, preferably 80 to 150[deg.] C. higher than the softening temperature of poly[theta]-butadiene, and ultraviolet rays are irradiated for a short period of time. Polybutadiene at its softening temperature, especially 150% below the softening temperature.
If the temperature is kept at a temperature higher than .degree. C. for a long period of time, the crosslinking reaction will proceed too much and this will cause a decrease in adhesiveness with polyolefins such as polypropylene, so it is better to avoid this. Conversely, irradiation with ultraviolet rays at temperatures below the softening temperature of polybutadiene has little effect. The reason for this is thought to be that the oxidation reaction due to ultraviolet irradiation is difficult to proceed unless the material is in a molten state. The method of irradiating ultraviolet rays is not particularly limited, but for example, if four 2KW ultraviolet lamps are used at the same time and the distance between the molten polybutadiene and the lamps is 10 cm, the irradiation time is preferably about 3 seconds.

In this case, if the irradiation time is 3 seconds or less, the adhesive strength decreases as the irradiation time decreases. On the contrary, when the irradiation time is 3 seconds or more, the adhesiveness improves as the irradiation time increases.
However, if crosslinking of polybutadiene progresses too much due to the heat generated during UV irradiation, modified polybutadiene/
Adhesion between polyethylene or polypropylene films is reduced. In the method of the present invention, in order to solve this problem, by mixing polyolefin such as ethylene/α-olefin copolymer with polybutadiene, the adhesion to polyethylene and polypropylene films is maintained regardless of the length of the ultraviolet irradiation time. making it good. In the present invention, metal is advantageously used as the substrate, but other plastic films, such as polyester, nylon, etc., can also be used.

In this case, the plastic film may be adversely affected by the heat generated during ultraviolet irradiation. In order to prevent this problem, it can be easily solved by installing a quartz plate between the ultraviolet lamp and the object to be irradiated. The base material and polyolefin may be partially or completely modified in order to improve adhesion or the like. The present invention will be specifically explained below using Examples and Comparative Examples.

Example 1 The ultraviolet irradiation conditions were as follows: four ultraviolet lamps each having a length of 30 cm and a power output of 2 KW were installed parallel to the direction of movement of the polybutadiene film.

The moving speed of the polybutadiene film is 10 m/min,
The irradiation distance is 10 cm (hereinafter, unless otherwise specified, this is the ultraviolet irradiation condition). 1.2 with a film thickness of 20μ
-Polybutadiene film (average molecular weight 140,000 to 150,000)
was attached to 15μ aluminum foil and heated at 200°C for 1 minute. This heated and molten polybutadiene is irradiated under the above irradiation conditions. A 90 μm polypropylene film is pressed onto the irradiated sample at 160° C. and 2 kg/cm 2 using a hot roll. As a result of measuring the aluminum/polypropylene laminate strength of the obtained sample, it was found to be 900 g/1
It showed good adhesion with a width of 5 mm. Examples 2 to 9 Tests were conducted according to Example 1 under the conditions shown in Table 1, and the results are shown in Table 1 as laminate strength and retort test.

Comparative examples 1-8 The test was carried out according to Example 1 under the conditions shown in Table 2.

Claims (1)

[Claims] 1. A method of adhering polyolefin to a base material such as metal, nylon, polyester, etc., characterized in that a polybutadiene layer irradiated with ultraviolet rays in a molten state is interposed between the polyolefin and the base material. Method. 2. The adhesion method according to claim 1, which uses a polybutadiene layer containing polyolefin. 3. The bonding method according to claim 1 or 2, in which 1,2-polybutadiene is used as the polybutadiene.