JP2757425B2 - adhesive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an adhesive. More specifically, the present invention relates to an adhesive which is suitable as an adhesive for a plastic container, can be easily molded, and has excellent easy peelability and punching properties.

[Problems to be Solved by Conventional Techniques and Inventions] In recent years, requirements for packaging materials for foods, medical products, and the like have been diversified, and the amount of plastic containers using easy-peeling lid materials has been reduced. It has grown significantly.
Conventionally, hot-melt type or heat-sealing lacquer has been used as an adhesive having easy peelability, but hot-melt type has problems in heat resistance, food hygiene, workability, etc. Since an organic solvent is used, the solvent may remain in the contents, which has a problem in food hygiene. Therefore, an extruded type mainly comprising an ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA) and a tackifier is becoming mainstream as an adhesive instead of these.

This extruded adhesive has a good balance of adhesive properties and processability, and is widely used as an easy peel material for various food containers. Such an easy peel material is generally compounded with a film of stretched polypropylene, nylon, polyester, polyvinyl chloride, paper, aluminum or the like via an adhesive or polyethylene, but has been pointed out as a drawback of the extrusion processing type. That is, when punching the lid material according to the shape of the container, when punching at a high speed, the punching performance deteriorates due to the toughness of the extrusion type, the size of elongation, etc. It has the problem of becoming

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in consideration of such points, and as a result, have found that the melt flow rate (JIS K-6730) is 0.5 to 50 g / 10.
min, 45-90% by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5-40% by weight, and a melt flow rate (JIS
K-6870) 0.6-30 g / 10 min of styrene polymer 5-35
It has been found that an adhesive composed of 5% by weight and 5-30% by weight of a tackifier has excellent workability, easy peelability and punching properties, and has reached the present invention.

EVA used in the present invention is obtained by randomly copolymerizing ethylene and vinyl acetate. The vinyl acetate content in the EVA is preferably from 5 to 40% by weight. If the vinyl acetate content is less than 5% by weight, the adhesion to the container may be poor, and if the vinyl acetate content exceeds 40% by weight, problems such as blocking properties and heat resistance may occur. EVA melt flow rate (hereinafter abbreviated as MFR) is 0.5-50g / 10min
Is preferred.

If the MFR is less than 0.5 g / 10 min or more than 50 g / 10 min, the processability is poor, which is not preferable. For the purpose of improving the heat resistance of the present composition, low-density polyethylene, medium-density polyethylene, high-density polyethylene, or the like may be added as a part of EVA. There is no problem if the amount of the polyethylene added is such that the vinyl acetate content falls within the range of 5 to 40% by weight based on the total amount of EVA and polyethylene.

The styrene-based polymer used in the present invention includes an impact-resistant styrene polymer obtained by grafting a styrene monomer onto a synthetic rubber such as polystyrene homopolymer, butadiene rubber, or styrene-butadiene rubber. They can be used alone or as a mixture. The styrene-based polymer preferably has an MFR of 0.6 to 30 g / 10 min. 0.6g MFR
If it is less than / 10 min, the processability is deteriorated, which is not preferable. When the MFR exceeds 30 g / 10 min, the punching property is deteriorated, which is not preferable.

The ratio of the EVA to the styrenic polymer is 45 to 90% by weight of EVA.
5-35% by weight of the styrene polymer. If the amount of the styrene-based polymer is less than 5% by weight, the punching property is poor, which is not preferable. On the other hand, if it exceeds 35% by weight, the processability is poor, which is not preferable.

Examples of the tackifier used in the present invention include aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, aromatic hydrocarbon resins, polyterpene resins, rosins, and styrene resins. Examples of aliphatic hydrocarbon resins, butene-1, butadiene, isobutylene, 1,3 C ₄ -C ₅ mono- or polymer comprising diolefins such pentadiene, alicyclic hydrocarbon resin An example of a Spent C ₄
-C ₅ diene component in the fraction were polymerized after cyclization dimerization resins, resins obtained by polymerization of cyclic monomers such as cyclopentadiene, resins or the like endocyclic hydrogenation of aromatic hydrocarbon resins, aromatic examples of family-based hydrocarbon resins, vinyl toluene, indene, alpha-resin whose main component is C ₂ vinyl aromatic hydrocarbons such as methyl toluene, examples of polyterpene resin, alpha-pinene polymer Rosins, such as rosin, polymerized rosin, hydrogenated rosin, .beta.-pinene polymer, dipentene polymer, terpene-phenol copolymer, hydrogenated terpene resin, .alpha.-pinene-phenol copolymer and the like.
Rosin glycerin ester and its hydrogenated or polymerized product, rosin pentaerythritol ester and its hydrogenated or polymerized product, and examples of the styrene-based resin include styrene-based homopolymer, styrene-olefin copolymer, vinyltoluene -Α-methylstyrene copolymer and the like. Among these tackifiers, aliphatic hydrocarbon resins and alicyclic hydrocarbon resins are preferred from the viewpoint of color tone, odor and the like.

The amount of the tackifier used is 5 to 30% by weight. If the amount of the tackifier is less than 5% by weight, the adhesion to the container is poor, which is not preferable. If the amount of the tackifier exceeds 30% by weight, blocking tends to occur, which is not preferable.

Although the adhesive of the present invention has good workability, adhesiveness and punching property, it is preferable to add a workability improver for the purpose of further improving the workability. Examples of such processability improvers include saturated or unsaturated fatty acid amides, fatty acid bisamides, inorganic fillers, hydrogenated castor oil, aliphatic metal salts, and the like, and these can be used alone or as a mixture.

The mixing method is not particularly limited, but is generally melt-mixed using a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader, a hot roll, or the like.

When using the adhesive of the present invention as a container adhesive, generally stretched polypropylene, nylon, polyester,
It is used as a composite material with a film substrate such as polyvinyl chloride, paper, and aluminum. The method of laminating these substrates is such that the adhesive is previously formed into a film by a molding machine such as inflation or casting, and then laminated by dry lamination or wet lamination.
Or after coating the base material with the anchor coating agent in advance, when extruding the polyethylene, sticking by sandwich lamination that the film is fed from the sand side, or after coating the base material with polyethylene in the same manner as the sandwich lamination, Bonding by tandem, in which an adhesive is extrusion-coated thereon, and the like can be given.

[Effect of the Invention] The adhesive according to the present invention has excellent processability, adhesiveness, and punching property as an adhesive for containers, and thus can be effectively used as an adhesive for various food containers. The adhesive according to the present invention can be said to be effective particularly when the lid material is punched at a high speed along the shape of the container.

[Examples] Next, the present invention will be described in more detail with reference to Examples.

Example 1 EV having a vinyl acetate content of 10% by weight and an MFR of 9 g / 10 min as an EVA
65% by weight of A (Ultracene 541 Tosoh), 20% by weight of a polystyrene homopolymer (manufactured by Denka Styrol GP-1 Denki Kagaku Kogyo) with MFR of 6.4g / 10min as a styrene-based polymer,
Alicyclic petroleum resin (Alcon P-100 as tackifier)
Arakawa Chemical) 15% by weight, erucamide (Nippon Seika) 0.08phr as a processability improver
Using a twin-screw extruder, the mixture was melt-mixed and pelletized under the condition that the resin temperature at the outlet was 180 ° C. Using a 25 mm laminator, this composition was previously coated with a urethane anchor coating agent on 35 μl aluminum foil, and then polyethylene was applied.
30 μm coating was performed on the polyethylene surface of the 20 μm extrusion coated laminate at an outlet temperature of 220 ° C.

The heat-sealing strength of the obtained laminate to polypropylene (PP) and high-impact polystyrene (HIPS) sheets was measured.

The punching property was measured using a continuous punching machine shown in FIGS. As shown in Fig. 1, the lid material is punched by placing the lid material 3 between the punching machines and closing the punching machine (Fig. 2) to reduce the lid material to a predetermined size on the surfaces 1 and 2. The lid material is formed into a cap shape by punching and further extruding the piston 4 continuously. The results are shown in Table 3. As for the punching performance, the ratio of defective products to non-defective products when 2000 pieces were punched was shown as a defective rate.

Example 2-3, Comparative Example 1-2 Except for using the adhesive composition shown in Tables 1 and 2, molding was performed in the same manner as in Example 1, and the heat seal strength and punching property were measured. The results are shown in Table 3.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a state before punching of a cover material of a continuous punching machine, and FIG. 2 is a schematic view showing a state immediately after punching. 1: One side of the punching machine 2: The other side of the punching machine 3: Lid 4: Piston

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C09J 123/00-123/08 C09J 131/00-131/04 C09J 125/00-125/08

Claims (1)

(57) [Claims] [Claim 1] Melt flow rate (JIS K-6730) 0.5
-50 g / 10 min, 45-90 wt% ethylene-vinyl acetate copolymer having a vinyl acetate content of 5-40 wt%, 5-35 wt% of a styrene polymer having a melt flow rate (JIS K-6870) of 0.6-30 g / 10 min % And a tackifier of 5 to 30% by weight.