JPH0127116B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new adhesive composition suitable for bonding styrene resin and metal, and more specifically, styrenic resin such as high impact polystyrene (HIPS), acrylonitrile-butadiene-styrene copolymer (ABS), and aluminum. , relates to a hot melt adhesive composition that can be used for lamination with metals such as iron. Generally, styrene resins have poor adhesion with other resins and materials, making it extremely difficult to select an adhesive. Adhesives commonly used at present include synthetic resins such as vinyl acetate resin and neoprene rubber, solvent-based adhesives in which synthetic rubber is dissolved in a solvent, and reaction-curing adhesives such as epoxy and polyester adhesives. In the case of the former, it is solvent-based and requires drying after adhesion, resulting in pollution and health and safety issues associated with handling the solvent, as well as the impact on quality due to chemical deterioration of the polystyrene resin surface caused by the solvent. Furthermore, it has various problems such as long open time for solvent removal. In addition, in the case of the latter reaction-curing type, it is necessary to mix and apply a curing agent, which requires ingenuity in the applicator, the pot life is short, the range of application of the adhesive is narrow, and the adhesive layer forms a three-dimensional structure. Therefore, it has various problems such as poor balance between shear adhesive strength and peel adhesive strength. The first object of the present invention is to provide a hot melt adhesive composition that provides sufficient adhesive strength for bonding styrene resin and metal. A second object of the present invention is to provide an adhesive composition that has a semi-permanent pot life, can be stored in a desired form such as film or pellet form, and allows the selection of the most suitable form for the adhesion process. It is in. A third object of the present invention is to provide an adhesive composition with a good balance between shear adhesive strength and peel adhesive strength. The present invention achieves the above objects,
The following three types of resins (a) Modified ethylene/acetic acid with an aromatic vinyl compound unit concentration of 10 to 70% by weight, obtained by subjecting an ethylene/vinyl acetate copolymer and an aromatic vinyl compound to graft reaction conditions. Vinyl copolymer from 10 to
60 to 95 parts by weight of an ethylene/vinyl acetate copolymer resin containing 100% by weight; (b) 5 to 40 parts by weight of a thermoplastic block elastic copolymer resin consisting of a conjugated diolefin and an aromatic vinyl compound;
parts by weight, and (c) modified ethylene with an ethylenically unsaturated carboxylic acid unit concentration of 0.01 to 10% by weight, obtained by subjecting an ethylene/vinyl acetate copolymer and an ethylenically unsaturated carboxylic acid to graft reaction conditions.・It is made by blending 5 to 50 parts by weight to 100 parts by weight of (a) + (b) of ethylene/vinyl acetate copolymer resin containing vinyl acetate copolymer at a ratio of 0.5 to 100% by weight. This is a characteristic adhesive composition. Hereinafter, the present invention will be explained in detail by dividing into each section. (1) Aromatic vinyl compound-modified ethylene/vinyl acetate copolymer This copolymer is obtained by subjecting an aromatic vinyl compound and an ethylene/vinyl acetate copolymer to graft reaction conditions, but preferably the following It can be obtained by the following method.
That is, 100 parts by weight of ethylene-vinyl acetate polymer particles with a vinyl acetate content of 2 to 50% by weight and a melt index of 0.1 to 200 g/10 minutes, 5 to 230 parts by weight of an aromatic vinyl compound, and a half-life of 10 hours. Add a radical polymerization initiator with a decomposition temperature of 50 to 130°C to obtain 100 parts by weight of the aromatic vinyl compound.
0.01 to 5.0 parts by weight in an aqueous medium in the presence of suspending agents used in aqueous suspension polymerization, such as polyvinyl alcohol, polyvinylpyrrolidone, methylcellulose, etc., or sparingly soluble inorganic substances, such as calcium phosphate, magnesium oxide, etc. at any concentration where the system is easily agitated (generally water
5 to 100 parts by weight of the polymer and aromatic vinyl compound are added to 100 parts by weight, and the mixture is stirred and dispersed.
This aqueous suspension is then heated within a range that does not substantially cause decomposition of the polymerization initiator used to impregnate the aromatic vinyl compound into the polymer particles. In impregnation treatment, the higher the heating temperature, the better from the viewpoint of promoting impregnation, but from the viewpoint of preventing the aromatic vinyl compound before impregnation from polymerizing alone due to premature decomposition of the polymerization initiator, the heating temperature is higher. The lower the temperature, the better, preferably between room temperature and 50°C. At least 80% by weight of the aromatic vinyl compound, preferably 90% by weight, under such temperature conditions.
Until more than % by weight of the aromatic vinyl compound droplets are impregnated or attached to the polymer particles, that is, free aromatic vinyl compound droplets are
The aqueous suspension is dissolved, preferably with stirring, in an amount of 1 to 5% by weight, preferably less than 20% by weight, preferably less than 10% by weight.
Leave it for about an hour. If the amount of unimpregnated aromatic vinyl compound is 20% by weight or more, independent vinyl polymer particles may be precipitated, and the vinyl polymer in the polymer particles may be non-uniformly dispersed. In addition, free aromatic vinyl compounds are impregnated into the polymer particles in the next polymerization step or attached to the surface of the polymer particles and polymerized, so the vinyl polymer particles are mixed with ethylene/vinyl acetate in the product. It is practically not recognized that it exists independently of the copolymer particles. A modified ethylene/vinyl acetate copolymer can be obtained by further heating the aqueous suspension prepared in this way to a high temperature to complete polymerization of the aromatic vinyl compound. In this case, the heating temperature should be such that sufficient decomposition of the polymerization initiator used occurs. but
Preferably, the temperature does not exceed 130°C. When the temperature exceeds 130°C, gel-like substances tend to form in the resulting modified polymer. Generally, a temperature of 50 to 130°C is suitable. As an aromatic vinyl compound, the general formula (In the formula, R ₁ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ₂ to _{R 6} are each independently a hydrogen atom,
chlorine atom or an alkyl group having 1 to 4 carbon atoms) such as styrene, nuclear-substituted styrene such as methylstyrene, dimethylstyrene, ethylstyrene, isopropylstyrene, and chlorstyrene, α-substituted styrene such as α-methyl Examples include styrene and α-ethylstyrene. Mixed systems such as styrene and acrylic ester, styrene and methacrylic ester, and styrene and acrylonitrile are also applicable. As the polymerization initiator, an oil-soluble one is used because it follows the technique of aqueous suspension polymerization. The polymerization initiator should have a decomposition temperature of 50-130°C to obtain a half-life of 10 hours. In particular, it is preferably within the range of 55 to 110°C. 50℃
If it is less than this, polymerization of the aromatic vinyl monomer will occur during the impregnation process, making it impossible to obtain a homogeneous product. 130
If the temperature is higher than 0.degree. C., the product will form a gel, which is unfavorable in terms of physical properties. This is considered to be because an intermolecular crosslinking reaction of the ethylene/vinyl acetate copolymer occurs as a result of excessively raising the temperature. Specific examples of the polymerization initiator include octanoyl peroxide, benzoyl peroxide, cyclohexanone peroxide, t-butyl peroxybenzoate, methyl ethyl ketone peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5
-dimethyl-2,5-dibenzoyl peroxyhexane, di-t-butyl-di-peroxyphthalate, lauroyl peroxide, t-butyl peroxypiparate, 3,5,5-trimethylhexanoyl peroxide, etc. Can be mentioned. The amount of the polymerization initiator used is 0.01 to 5.0 parts by weight per 100 parts by weight of the aromatic vinyl compound. The aromatic vinyl compound-modified ethylene/vinyl acetate copolymer thus obtained has an aromatic vinyl compound unit concentration of 10 to 70% by weight,
In the present invention, this is used as an ethylene/vinyl acetate copolymer containing 10 to 100% by weight. If the aromatic vinyl compound concentration of the aromatic vinyl compound-modified ethylene/vinyl acetate copolymer is less than 10% by weight, good compatibility with the above component (b) will not be obtained, and the composition will not be suitable for polystyrene. Sufficient adhesive strength to the resin cannot be obtained. On the other hand, if it exceeds 70% by weight, the adhesive itself becomes hard, which impairs its physical properties as an adhesive. Furthermore, if the blending amount of component (a) is less than 10% by weight, there will be no improvement in adhesive strength, especially for polystyrene resins, and the compatibility with component (b) will also deteriorate, resulting in layer peeling. There is a tendency to cause such things. (2) Thermoplastic block elastic body This is a thermoplastic block elastic body whose general formula consisting of a conjugated diolefin and an aromatic vinyl compound is represented by the following formula, and is produced, for example, by the method disclosed in Japanese Patent Publication No. 17492/1983. (A-B)n+1, B-(A-B)n+1, A-B-(B-A)n+1 and/or A-(B-A)n. Here, A represents an inelastic polymer block made of an aromatic vinyl compound, and B represents an elastic polymer block of conjugated diolefin. Further, n represents an integer from 1 to 20, and the proportion of the A block to the entire molecule is 1 to 50% by weight. The average molecular weight of this elastic body is 10,000 to 1,000,000
Preferably it is 50,000 to 250,000. The conjugated diolefin used in the present invention includes 1,3-
Butadiene, isoprene, n-1-3-pentadiene, etc. are used. Further, as the aromatic vinyl compound, styrene, methylstyrene, dimethylstyrene, etc. are used. Incidentally, a thermoplastic block elastomer obtained by hydrogenating a conjugated diolefin polymer block is also applicable to the present invention. (3) Ethylene-vinyl acetate copolymer modified with ethylenically unsaturated carboxylic acid or its anhydride, preferably an ethylene-vinyl acetate copolymer with a vinyl acetate content of 2 to 50% by weight and a melt index of 0.1 to 200 g/10 min.
A vinyl acetate copolymer is modified with an ethylenically unsaturated carboxylic acid or its anhydride, and the latter is modified by graft polymerization. Ethylenically unsaturated carboxylic acids or their anhydrides include acrylic acid, maleic acid, itaconic acid,
Hymic acid or their anhydrides are applied. In particular, it is preferable to use maleic anhydride and acrylic acid. To modify the ethylene/vinyl acetate copolymer with these ethylenically unsaturated carboxylic acids or their anhydrides, there are several methods: irradiation with ionizing radiation, ultraviolet rays, etc., methods using radical initiators, oxygen, ozone, heat, etc. Graft polymerization can be carried out by various initiation methods, such as peroxidation by the action of oxidation, or use of heat and shear force in a kneader. The graft polymerization can be carried out by any known method such as in a solution state, slurry state, or melt state. The modified ethylene/vinyl acetate copolymer thus obtained has an ethylenically unsaturated carboxylic acid unit concentration of 0.01 to 10% by weight, and in the present invention, the concentration is 0.5 to 100% by weight. It is used as an ethylene/vinyl acetate copolymer containing If the concentration of ethylenically unsaturated carboxylic acid units in this modified ethylene/vinyl acetate copolymer is less than 0.01% by weight, sufficient adhesive strength cannot be obtained, especially for metals, whereas if it exceeds 10% by weight, If you try to obtain it, it will cause cross-linked gel and deterioration, which is not preferable. In addition, the amount of this added to component (c) is 0.5% by weight.
If it is less than this, the adhesive strength, especially to metals, will be poor, which is undesirable. When modifying with an ethylenically unsaturated carboxylic acid or its anhydride, an unmodified ethylene/vinyl acetate copolymer may remain.
Such an unmodified ethylene/vinyl acetate copolymer is treated as one blended with the above-mentioned modified ethylene/vinyl acetate copolymer. The adhesive composition of the present invention exhibits excellent adhesion to polystyrene resins in particular. Here, the polystyrene resin is a resin containing at least 25% by weight of a structural unit represented by the following general formula. (Here, R is a hydrogen atom or a methyl group, Z is a halogen atom or a methyl group, and p is 0 or 1
It is an integer of ~3. ) Specifically, polystyrene, rubber-modified polystyrene, styrene/acrylonitrile copolymer, styrene/butadiene/acrylonitrile copolymer,
Examples include homopolymers and copolymers of styrene and its derivatives, such as styrene/butadiene/methyl methacrylate copolymer, styrene/α-olefin rubber/acrylonitrile copolymer, and styrene/α-methylstyrene copolymer. It will be done. Especially polystyrene, rubber-modified polystyrene,
Styrene-butadiene-acrylonitrile copolymer is preferred. The constituent components of the adhesive composition of the present invention described above are formulated as follows. That is, (a) an ethylene/vinyl acetate copolymer 60 to 95 containing a modified ethylene/vinyl acetate copolymer having an aromatic vinyl compound unit concentration of 10 to 70% by weight in a proportion of 10 to 100% by weight;
and (c) ethylenically unsaturated carboxylic acid unit concentration relative to 100 parts by weight of a resin consisting of (b) a thermoplastic block elastomer of 5 to 40% by weight consisting of a conjugated diolefin and an aromatic vinyl compound. is 0.01~10% by weight
of modified ethylene/vinyl acetate copolymer from 0.5 to 100
It contains 5 to 50 parts by weight of ethylene/vinyl acetate copolymer in a proportion of 5 to 50 parts by weight. Here, if component (a) exceeds 95% by weight, that is, component (b) is less than 5% by weight, the adhesive strength, especially for polystyrene resins, will not be sufficient; If the amount of component (b) is less than 40% by weight, extrusion moldability may be impaired. Also,
If component (c) is less than 5 parts by weight, the adhesion to metals will be particularly poor, while if it exceeds 50 parts by weight, not only will the effect of modifying the adhesive strength with metals be saturated, but conversely, the adhesive strength with metals will be saturated. This is undesirable because the adhesive strength of the material decreases. As described above, the present invention includes a homogeneous mixture of three components each having different adhesive properties,
This is an adhesive composition that exhibits extremely excellent adhesion to both polystyrene resins and metals, and because of its homogeneity, it can be melt-kneaded and freely formed into films, sheets, granules, and pellets. . As the melt-kneading method, known methods such as an extruder, Banbury, and roll can be used. The adhesive composition homogenized by this type of method can be formed into a film by a known film forming method such as an inflation method or a T-die method, and used as a film adhesive. Alternatively, it can be made into pellets using an extruder or the like and used as a pellet-like adhesive, or it can be pulverized by known methods such as mechanical pulverization or chemical pulverization and used as a powdered adhesive. can be stacked. Alternatively, the adhesive composition of the present invention and the polystyrene resin may be laminated by a known co-extrusion method such as in-die or outside-die lamination, and metal may be laminated by pressure on the surface of the adhesive layer. The heating temperature during lamination is above the melting point of each resin and below the decomposition temperature, that is, 70 to 300°C, preferably 100 to 300°C.
The temperature is 250° C., and the pressure is preferably 1 Kg/cm ² or more and 150 Kg/cm ² or less, preferably 10 to 50 Kg/cm ² . Furthermore, in view of the above performance, it is obvious that the adhesive of the present invention can also be used as an adhesive between polystyrene resins or between metals. Further, the bonding does not necessarily have to be done by solid adhesive (laminated type), and depending on the case, it is also possible to do point bonding at the necessary locations. Examples of the present invention will be described below. Example 1 20 kg of pure water and 600 g of tribasic calcium phosphate and 0.65 g of sodium dodecylbenzenesulfonate as suspending agents were added to an autoclave with a capacity of 50 mm to form an aqueous medium, and ethylene/vinyl acetate copolymer (MI12 °, density 0.948, vinyl acetate content
20% by weight) particles were suspended by stirring. Separately, 8 g of benzoyl peroxide as a polymerization initiator
and 4 g of t-butyl peroxybenzoate were dissolved in 4 kg of styrene (60% by weight based on the ethylene/vinyl acetate copolymer), and this was added to the suspension system, and the temperature inside the autoclave was raised to 45 ° C. The temperature was maintained for 3 hours to impregnate styrene containing a polymerization initiator into the ethylene/vinyl acetate copolymer particles. This aqueous suspension was heated to 80°C and maintained at this temperature for 5 hours and then at 125°C for 5 hours to complete polymerization. It was confirmed that polystyrene was almost quantitatively present at 60% by weight in the obtained modified particles. In addition, 2,5-
Thoroughly mix 0.6% by weight of dimethyl-hexane-2,5-dihydroperoxide and 1.0% by weight of maleic anhydride using a Henschel mixer to form a 40mm
Extrusion temperature 150℃ using φ extruder (L/D=28)
It was made into pellets. After crushing the obtained pellets,
After sufficiently extracting unreacted maleic anhydride with acetone, it was confirmed by infrared absorption spectrum that 0.76% by weight of maleic anhydride had been added. The styrene-modified ethylene-vinyl acetate copolymer and maleic anhydride-modified ethylene-vinyl acetate copolymer obtained as above, the styrene-butadiene block elastomer (Ciel Kagaku Co., Ltd., Califrex TR-1102) and /or blend a predetermined amount of unmodified ethylene/vinyl acetate copolymer,
The mixture was melt-kneaded using a 40 mmφ extruder at a temperature of 160°C to obtain homogeneously mixed pellets. This pellet was formed into a 50μ thick film using a T-die film molding machine, and using this film as an adhesive, a 1mm thick sheet of ABS resin (Mitsubishi Montmont, Toughflex 410) and 50μ thick aluminum foil were bonded together. It was thermocompressed using a heat sealer. Heat sealing conditions were: temperature 160℃, pressure 1.4Kg/cm ² , time 10
Seconds. The crimped area is 200mm x 15mm. The ABS resin/aluminum foil laminate thus obtained was cut to a width of 20 mm and subjected to a 180°C peel test (peeling speed 500 mm/min). The results are shown in Table-1. Comparative Example 1 Table 1 shows the results of using only ethylene/vinyl acetate copolymer as the adhesive in Example 1. Comparative Example 2 Table 1 shows the results of using only the styrene-modified ethylene/vinyl acetate copolymer as the adhesive in Example 1. Comparative Example 3 In Example 1, 80% by weight of the styrene-modified ethylene/vinyl acetate copolymer and a block elastomer (Ciel Kagaku Co., Ltd., Califrex,
TR-1102) The results using a 20% by weight blend are shown in Table-1. Comparative Example 4 Table 1 shows the results of using the maleic anhydride-modified ethylene/vinyl acetate copolymer as the adhesive in Example 1. Comparative Example 5 In Example 1, a blend of 100 parts by weight of the styrene-modified ethylene/vinyl acetate copolymer and 20 parts by weight of the maleic anhydride-modified ethylene/vinyl acetate copolymer was used as the adhesive. It is shown in Table-1. Example 2 A styrene/acrylonitrile modified ethylene/vinyl acetate copolymer polymerized using 3 kg of styrene and 1 kg of acrylonitrile in Example 1,
Styrene-butadiene block elastic body (Asahi Kasei,
Toughprene) and maleic anhydride-modified ethylene.
An adhesive blended with a predetermined amount of vinyl acetate copolymer was extrusion laminated to a thickness of 30μ onto a 50μ aluminum foil at an extrusion temperature of 210°C using a 50mmφ laminator. Aluminum foil coated with this adhesive and a 0.5 mm thick sheet of ABS resin were thermocompressed using a press molding machine at a temperature of 200°C and a pressure of 10 kg/ ^cm2 , and a 20 mm wide 180° peel test ( Peeling speed 500
mm/min). The results are shown in Table-2. This product was also subjected to a 90° bending test at a low temperature of 0°C, but no peeling phenomenon was observed at the bent R portion, confirming that it had good adhesive properties even at low temperatures. Comparative Example 6 Table 2 shows the results of using a blend of 100 parts by weight of ethylene/vinyl acetate copolymer and 20 parts by weight of maleic anhydride-modified ethylene/vinyl acetate copolymer as the adhesive in Example 2. . Example 3 Ethylene-vinyl acetate copolymer (MI4, density
0.938, vinyl acetate content 15% by weight) was suspended in toluene, 3 parts of acrylic acid was added to this,
Stir for 30 minutes at room temperature. Thereafter, the temperature was raised to 100° C. while stirring, and 2 parts of 3,5,5-trimethylhexanoyl peroxide was diluted with toluene and added dropwise over 30 minutes. 100℃ for 2 hours and 30 minutes after dropping
The reaction was continued by maintaining the temperature at After the reaction was completed, the polymer was reprecipitated using excess acetone, unreacted monomers were thoroughly removed, and a powdery polymer was obtained by centrifugation. The acrylic acid content of this polymer was determined by infrared absorption spectrum.
0.9% by weight of acrylic acid was added. The thus obtained acrylic acid-modified ethylene/vinyl acetate copolymer, the ethylene-modified ethylene/vinyl acetate copolymer used in Example 1, and the styrene/butadiene block elastomer were blended in predetermined amounts to form a 40 mmφ
The mixture was melt-kneaded at 190°C using an extruder (L/D=28) to obtain homogeneous pellets. This pellet was molded into a film with a thickness of 50μ using a T-die film molding machine, and this film was used as an adhesive to form rubber-modified polystyrene (Mitsubishi Monsanto Co., Ltd.,
A 1 mm thick sheet of Dialex HT190) and metal foil were press-molded under bonding conditions of 140°C and 40°C.
Kg/cm ² and bonded for 3 minutes, and the 180° peel strength was measured. The results are shown in Table-3. (As foil, steel foil,
(using Al foil)

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Claims (1)

[Claims] 1 (a) Modified ethylene with an aromatic vinyl compound unit concentration of 10 to 70% by weight, obtained by subjecting an ethylene/vinyl acetate copolymer and an aromatic vinyl compound to graft reaction conditions. Vinyl acetate copolymer 10
60 to 95 parts by weight of an ethylene/vinyl acetate copolymer resin containing ~100% by weight; (b) 5 to 40 parts by weight of a thermoplastic block elastic copolymer resin comprising a conjugated diolefin and an aromatic vinyl compound;
parts by weight, and (c) modified ethylene with an ethylenically unsaturated carboxylic acid unit concentration of 0.01 to 10% by weight, obtained by subjecting an ethylene/vinyl acetate copolymer and an ethylenically unsaturated carboxylic acid to graft reaction conditions.・5 to 50 parts by weight of ethylene/vinyl acetate copolymer resin (a) + (b) containing 0.5 to 100% by weight of vinyl acetate copolymer to 100 parts by weight of (a) + (b). Characteristic adhesive composition.