JPS6246354B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improving interlaminar strength in a laminate of an adhesive resin layer and a polystyrene resin layer used as one of the resin layers of a multilayer film or multilayer sheet consisting of two or more resin layers. Various methods have been proposed in the past for multilayering polystyrene resin. For example, there is a dry lamination method in which a polystyrene resin and another resin are laminated using an adhesive. This method complicates the process by increasing the adhesive application process and drying process (solvent removal process), and the quality is affected by chemical deterioration of the polystyrene resin surface due to the solvent contained in the adhesive. This is undesirable because there are concerns about the use of adhesives, as well as pollution and health and safety issues associated with the use of adhesives. Still another method is multilayering by coextrusion. In order to improve the adhesion between layers, ethylene/vinyl acetate copolymer resin, ethylene/vinyl ester copolymer resin, etc. are used, or styrene/butadiene block copolymer rubber, etc. is used with polystyrene resin and other resins. There is a method of interposing an adhesive layer between the two. However, when using ethylene/vinyl acetate copolymer resin or ethylene/vinyl ester copolymer resin, the interlaminar strength is unsatisfactory, and when using styrene/butadiene block copolymer rubber, its own fluidity is significantly inferior. In addition, because of poor thermal stability, there are various problems with moldability, such as crosslinking reaction occurring due to heat during lamination, making it difficult in practice. The purpose of the present invention is to solve the above-mentioned problems, and to provide adhesive properties for polystyrene resins as adhesives or intermediate layers for laminates with polystyrene resins, or as adhesives or intermediate layers for laminates between polystyrene resins and other resins. The object of the present invention is to provide a resin with good adhesive properties. That is, the present invention provides a polystyrene resin layer, (a) 100 to 10 parts by weight of a modified ethylene/vinyl acetate copolymer resin obtained by the following modification method, and (b) ethylene/vinyl acetate copolymer resin.
This polystyrene resin laminate is characterized by comprising at least two layers, including an adhesive resin layer comprising 0 to 90 parts by weight of a vinyl acetate copolymer resin. Modification method: 100 parts by weight of ethylene/vinyl acetate copolymer resin particles, 5 to 200 parts by weight of aromatic vinyl monomer, and a decomposition temperature of 50 to 50 to obtain a half-life of 10 hours.
An aqueous suspension containing 0.01 to 5.0 parts by weight of a radical polymerization initiator per 100 parts by weight of an aromatic vinyl monomer at 130°C is heated under conditions that do not substantially cause decomposition of the radical polymerization initiator. After impregnating the ethylene/vinyl acetate copolymer resin particles with aromatic vinyl monomer until the amount of free aromatic vinyl monomer becomes less than 20% by weight, the temperature of this aqueous suspension is raised to 50 to 130°C. The polymerization of the aromatic vinyl monomer is completed to obtain a modified ethylene/vinyl acetate copolymer resin. In addition, as each good form of the present invention, based on 100 parts by weight of the composition of (a) modified ethylene/vinyl acetate copolymer resin and (b) ethylene/vinyl acetate copolymer resin,
Furthermore, (c) consists of an inelastic polymer block A made of an aromatic vinyl compound and an elastic polymer block B made of a conjugated diolefin, (A-B) _o+1 , B-
(A-B) _o+1 or A-(B-A) _o (where n is 1
There is provided a laminate using an adhesive resin containing 1 to 150 parts by weight of a thermoplastic block elastic body exhibiting a block structure (an integer of 20 to 20). The present invention will be explained in detail below by dividing it into each section. (1) Modified ethylene/vinyl acetate copolymer resin Ethylene/vinyl acetate copolymer resin, which is the base resin for modification, can be produced by high-pressure polymerization at 1000 to 3000 atmospheres or by solution or emulsion polymerization at 100 to 400 atmospheres. Any conventional manufacturing method may be used. If the vinyl acetate content of this ethylene/vinyl acetate copolymer resin is 2 to 50% by weight, a modified resin that achieves the object of the present invention can be obtained, but it is preferably in the range of 5 to 45% by weight. There is no particular limit to the molecular weight, and the melt index (190℃, 2.16Kg load) is 0.1 to 200.
g/10 min is used. 100 parts by weight of the resin particles, 5 to 200 parts by weight of the aromatic vinyl monomer, and a radical polymerization initiator having a decomposition temperature of 50 to 130°C to obtain a half-life of 10 hours, per 100 parts by weight of the aromatic vinyl monomer. 5.0 parts by weight is stirred into an aqueous medium in the presence of a suspending agent used in aqueous suspension polymerization, such as polyvinyl alcohol, polyvinylpyrrolidone, methyl cellulose, etc., or a sparingly soluble inorganic substance, such as calcium phosphate, magnesium oxide, etc. Addition and dispersion is carried out at any concentration easily accomplished (generally from 5 to 100 parts by weight of resin and aromatic vinyl monomer to 100 parts by weight of water). Next, a polymerization treatment is carried out, but prior to that, this aqueous suspension is heated within a range that does not substantially cause decomposition of the polymerization initiator used to impregnate the aromatic vinyl monomer into the resin particles. For impregnation treatment, higher heating temperatures are better from the point of view of promoting impregnation.
Since the aromatic vinyl monomer before impregnation polymerizes alone due to premature decomposition of the polymerization initiator, in order to prevent this, the heating temperature should be lower, preferably from room temperature to 50°C. Under such temperature conditions, until at least 80% by weight, preferably at least 90% by weight, of the aromatic vinyl monomer is impregnated or attached to the resin particles, that is, the free aromatic vinyl monomer droplets remain at 20% by weight, preferably at least 90% by weight. is 10
The aqueous suspension is allowed to stand, preferably with stirring, for about 1 to 5 hours until it reaches less than % by weight. 20% by weight unimpregnated aromatic vinyl monomer
In the above case, there is a possibility that independent vinyl polymer particles will precipitate, and the dispersion of the vinyl polymer in the resin particles will become non-uniform. In addition, in the next polymerization step, the free aromatic vinyl monomer is impregnated into the resin particles or attached to the surface of the resin particles and polymerized. In fact, it cannot be recognized that it exists independently. A modified ethylene/vinyl acetate copolymer resin is obtained by further heating the thus prepared aqueous suspension to a high temperature to complete polymerization of the aromatic vinyl monomer. In this case, the heating temperature should be such that sufficient decomposition of the polymerization initiator used occurs. However, it is preferable not to exceed 130°C. When the temperature exceeds 130°C, gel-like substances tend to form in the resulting modified resin. Generally 50~130℃
temperature is appropriate. The aromatic vinyl monomer has the general formula

[Formula] (In the formula, R ₁ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ₂ to _{R 6} are a hydrogen atom, a chlorine atom, or an alkyl group having 1 to 4 carbon atoms, respectively.) Monomers such as styrene, nuclear substituted styrenes such as methylstyrene, isopropylstyrene, chlorstyrene,
α-substituted styrene such as α-methylstyrene, α
Examples include 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. According to a feature of the invention, the polymerization initiator has a decomposition temperature of 50 to obtain a half-life of 10 hours.
Must be ~10°C. especially 55
It is preferably within the range of ~110°C. In this case, if the decomposition temperature is lower than 50°C, polymerization of the aromatic vinyl monomer will occur during the impregnation process, making it impossible to obtain a homogeneous product. Furthermore, if the temperature is higher than 130°C, the product will form a gel, which is unfavorable in terms of physical properties.
This results in excessive temperature rise, resulting in the ethylene
This is thought to be due to an intermolecular crosslinking reaction of the vinyl acetate copolymer resin. Specific examples of the initiator include octanoyl peroxide, benzoyl peroxide, cyclohexanone peroxide, t-butyl peroxybenzoate, methyl ethyl ketone peroxide, 2,5-dimethyl-2,5-dibenzoyl peroxyhexane, di- Examples include t-butyl-di-peroxyphthalate, lauroyl peroxide, t-butyl peroxypivalate, and 3,5,5-trimethylhexanoyl peroxide. The amount of polymerization initiator used is based on the aromatic vinyl monomer.
The amount is 0.01 to 5.0 parts by weight per 100 parts by weight. (2) Ethylene/vinyl acetate copolymer resin for blending High pressure polymerization method under 1000 to 3000 atmospheres or 100 to 400 atmospheres
Any conventional manufacturing method such as a solution under atmospheric pressure or an emulsion polymerization method may be used.
The vinyl acetate content of this ethylene/vinyl acetate copolymer resin is 2 to 50% by weight, preferably 10% by weight.
~35% by weight. The molecular weight is not particularly limited, but from the viewpoint of extrusion moldability, it is preferable to have a melt index (190 DEG C., 2.16 kg load) of 0.1 to 30 g/10 min. (3) 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. 42-17492. (A-B) _o+1 , B- (A-B) _o+1 or A-
(B-A) _o Here, A is a polymer block made of an aromatic vinyl compound, B is a conjugated diolefin polymer block, n is an integer from 1 to 20, and the proportion of 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 50,000 to 250,000. The conjugated diolefin used in the present invention is 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. (4) Polystyrene-based resin The polystyrene-based resin to which the adhesive resin of the present invention is particularly advantageously applied is a resin containing at least 25% by weight or more of a structural unit represented by the following general formula.

[Formula] (Here, R represents a hydrogen atom or a methyl group, Z represents a halogen atom or a methyl group, and p is 0 or an integer of 1 to 3.) Specifically, polystyrene, rubber-modified polystyrene, styrene, etc. Acrylonitrile copolymer resin, styrene/butadiene/acrylonitrile copolymer resin, styrene/butadiene/methyl methacrylate copolymer resin, styrene/α-olefin rubber/acrylonitrile copolymer resin,
Examples include homopolymer resins and copolymer resins of styrene and its derivatives, such as styrene/α-methylstyrene copolymer resin. Particularly preferred are polystyrene/rubber-modified polystyrene and styrene/butadiene/acrylonitrile copolymer resins. The adhesive resin described above exhibits excellent interlaminar strength when laminated with a polystyrene resin. Further, in a multilayer film or sheet having a polystyrene resin layer, the polystyrene resin layer can be used as an adhesive layer between the polystyrene resin layer and other resin layers. For example, on a laminate in which a polystyrene resin layer is laminated with a resin made of the modified ethylene/vinyl acetate copolymer resin, ethylene/vinyl acetate copolymer resin, and thermoplastic block elastic body, polyethylene or ethylene is further layered. A multilayer laminate having excellent interlaminar strength is provided, in which copolymer resins containing polypropylene (including ethylene/vinyl acetate copolymer resins), polypropylene or propylene-containing copolymer resins, or polystyrene resins are laminated. The production of laminates using the adhesive resin described above does not require the conventional dry lamination method, but can be produced using known co-extrusion methods such as in-die lamination method and outside-die lamination method, making it easier to manufacture than conventional methods. This method was simplified, and also solved the problems of pollution and hygiene caused by adhesives, which were problems with the dry lamination method. In addition to these methods, any molding method under melt pressure, such as thermocompression bonding using a press, can be used. The pressure condition at this time is 1
Requires more than Kg/cm ² . Further, the adhesive resin described above does not necessarily need to be used as a solid adhesive (laminated type), but can also be used in a spot adhesive form if necessary. Hereinafter, the present invention will be explained with reference to Examples. Example 1 20 kg of pure water, 600 g of tribasic calcium phosphate and 0.6 g of sodium dodecylbenzenesulfonate as suspending agents were added to an autoclave with a capacity of 50 mm to form an aqueous medium, and an ethylene/vinyl acetate copolymer resin (MI .12.0, density 0.948, vinyl acetate content 20% by weight) particles were suspended by stirring. Separately, 8 g of benzoyl peroxide and 4 g of t-butyl peroxybenzoate as polymerization initiators.
was dissolved in 4 kg of styrene (67 parts per 100 parts of ethylene/vinyl acetate copolymer resin), this was added to the suspension system, the temperature inside the autoclave was raised to 65°C, and the temperature was maintained at this temperature for 3 hours. Styrene containing a polymerization initiator was impregnated into ethylene/vinyl acetate copolymer resin particles. This aqueous suspension was heated to 80°C, maintained at that temperature for 5 hours, and further maintained at 125°C for 5 hours to complete polymerization. It was confirmed that 67 parts by weight of polystyrene was almost quantitatively present in the obtained improved particles. Press molding (temperature
A sheet with a thickness of 1 mm was produced at 160° C. and a pressure of 150 Kg/cm ² ). Separately, a 1 mm thick sheet of rubber-modified polystyrene (Dialex HT-190, Mitsubishi Monsanto) was similarly press-molded (temperature 230°C, pressure 150 kg/cm ² ). Both sheets were laminated and molded using a press molding machine at a temperature of 210℃ and a pressure of 20Kg/
It was crimped under the condition of ^cm2 . This laminated sheet was cut to a width of 10 mm and a 180° peel test was conducted. The results are shown in Table-1. Furthermore, the results of a similar test using a blend of a specified amount of modified resin (modified EVA) and ethylene/vinyl acetate copolymer resin (EVA, MI30, density 0.960, vinyl acetate content 33% by weight) are shown. -1
Shown below. Comparative Example 1 Table 1 shows the results of a test similar to Example 1 using ethylene/vinyl acetate copolymer resin (EVA).

[Table] Example 2 The modified resin (modified EVA) obtained in Example 1 and ethylene-vinyl acetate copolymer resin (EVA) were blended in any ratio, and a 100 μ film was produced using a 30 m/m film molding machine. was created. A 1 mm thick sheet of ABS resin (Toughflex 410, Mitsubishi Monsanto), which was separately produced by press molding, and the above film were thermocompression bonded using a heat sealer. Heat sealing conditions are temperature 160℃, pressure 1.4Kg/cm ² , time
It is 10 seconds. The crimping area is 200 x 15 mm. This laminate was cut to a width of 20 mm and a 180° peel test was performed (peel speed 500 mm/min). The results are shown in Table-2. Comparative Example 2 In Example 2, ethylene/vinyl acetate copolymer resin, ethylene/methacrylic acid copolymer resin (melt index 40 g/10
The results are shown in Table 2.

[Table] Example 3 A modified ethylene/vinyl acetate copolymer resin modified with 150 parts by weight of styrene was produced in the same manner as in Example 1. On the other hand, AS resin (Mitsubishi Monsanto SAN)
-C) using the famous SJ-35 injection molding machine, molding temperature 260℃, mold temperature 60℃, injection pressure 1000Kg/
A square sheet of 100 x 100 x 1 mm was produced under cm ² conditions. Furthermore, the thickness of the same mold was changed to 2 mm, a 1 mm sheet of AS resin was fixed in the mold, and the modified resin was injection molded on top of it to obtain a laminated injection molded sheet of AS resin and the modified resin. Ta. The molding conditions were a molding temperature of 220°C, a mold temperature of 40°C, and an injection pressure of 750 kg/cm ² . An impact was applied to this laminated sheet using a Dupont impact tester, and the state of peeling between the two layers was observed. Comparative Example 3 A laminated sheet with AS resin was prepared using ethylene/vinyl acetate copolymer resin in the same manner as in Example 3, and the interfacial state under impact was observed. The results are as follows. A dart was applied to the AS resin side of the laminated sheet, and the energy value when the phenomenon of peeling between the two layers was observed was measured. Example 3: 300 g-cm Comparative Example 3: 50 g-cm or less In the laminated sheet of Example 3, even if cracks occurred in the AS resin layer, no interfacial peeling was observed, and the adhesive was extremely strong. I found out that there was. Example 4 50% by weight of the modified ethylene/vinyl acetate copolymer resin obtained in Example 3 and 50% by weight of ethylene/vinyl acetate copolymer resin (MI.30, density 0.960, vinyl acetate content 33% by weight) were blended. A three-layer coextrusion sheet of rubber-modified polystyrene (Dialex HT-190, Mitsubishi Monsanto Co., Ltd.) and ABS resin (Tufflex 461, Mitsubishi Monsanto Co., Ltd.) was prepared using the resulting material as an intermediate adhesive layer. The die temperature of coextrusion molding equipment is
The temperature was 210°C, and the thickness of the sheet was HIPS/adhesive layer/ABS resin = 14/1/4. The interlaminar strength of this laminated sheet was measured using a tensile tester. The results are shown in Table-3. Comparative Example 4 The interlaminar strength of a laminated sheet produced by the method of Example 4 using an ethylene/vinyl acetate copolymer resin (MI 12.0, density 0.948, vinyl acetate content 20% by weight) as an adhesive layer was measured. The results are shown in Table-3.

[Table] Example 5 Blending a predetermined amount of the modified resin (modified EVA) obtained in Example 1, ethylene/vinyl acetate copolymer resin (EVA), and styrene/butadiene block elastomer (Ciel Kagaku Kaliflex TR1102). The mixture was then melt-kneaded in a 40 mmφ extruder at a temperature of 160°C to obtain pellets in which the three components were homogeneously mixed. Using this pellet, a 100μ film was produced using a 30mmφ inflation film molding machine. A 1 mm thick sheet of ABS resin (Toughflex 410, manufactured by Mitsubishi Monsanto Co., Ltd.), which had been separately produced by press molding, and the above film were thermocompression bonded using a heat sealer. Heat sealing conditions are temperature 160℃, pressure 1.4Kg/cm ² , time 10
Seconds. The crimping area is 200 x 15 mm. This laminate was cut to a width of 20 mm and subjected to a 180° peel test (peel speed 500 mm/min). Table 4 shows the results.
Shown below. Comparative Example 5 Table 4 shows the results of using ethylene/vinyl acetate copolymer resin alone and a mixture of ethylene/vinyl acetate copolymer resin and styrene/butadiene block elastomer instead of the modified resin in Example 3. show.

[Table] Example 6 Similar to Example 5, predetermined amounts of modified EVA, EVA, and styrene-butadiene block elastomer (Tuffprene, manufactured by Asahi Kasei Corporation) were blended and melt-kneaded at a temperature of 160°C in a 40 mmφ extruder. A pellet in which the three components were homogeneously mixed was obtained. These pellets and rubber-modified polystyrene (Mitsubishi Monsanto Dialex)
HT-190) and low-density polyethylene (MI0.5, density 0.926), press sheets of 0.5 mm, 1.0 mm, and 0.5 mm, respectively, were produced by press molding, and these were rubber-modified polystyrene/the modified Overlaid on a three-layer structure of resin/low-density polyethylene, press molded at a temperature of 200℃ and a pressure of 20Kg/cm ²
A three-layer laminated sheet was obtained by pressure bonding under the following conditions. This sheet was cut to a width of 10 mm, and a 180° peel test was conducted between the rubber-modified polystyrene and the modified resin surface. The results are shown in Table-5. Note that it was impossible to measure the interlaminar strength between the modified resin and low-density polyethylene because the adhesion was strong and caused cohesive failure of the materials. In addition, using this laminated sheet, a small container (L/
D=0.5) was molded. Fill this container with water,
A drop test was conducted in which the bottom of the container collided with the concrete floor from a height of 1 m, and the deformation of the container was observed. The results are shown in Table-5. Comparative Example 6 In the layer structure of rubber-modified polystyrene/adhesive layer/low-density polyethylene in Example 2, the adhesive layer
Table 5 shows the results using EVA alone and a mixture of EVA and styrene-butadiene block elastomer. Furthermore, similar evaluation results for the rubber-modified polystyrene/low-density polyethylene two-layer laminate sheet are also shown in Table 5.

[Table] Example 7 Modified ethylene/vinyl acetate copolymer resin modified with 150 parts by weight of styrene obtained in Example 3, and modified ethylene/vinyl acetate copolymer resin modified with 100 parts by weight of styrene and 50 parts by weight of acrylonitrile. Vinyl acetate copolymer resins were obtained. These modified ethylene/vinyl acetate copolymer resins, ethylene/vinyl acetate copolymer resins (MI30, density 0.960, vinyl acetate content 33% by weight) and styrene/butadiene block elastomer (Ciel Chemical Co., Ltd. Califrex TR1102) are blended in predetermined amounts. A three-layer coextrusion sheet of rubber-modified polystyrene (Dialex TH-190, Mitsubishi Monsanto Co., Ltd.) and ABS resin (Tufflex 461, Mitsubishi Monsanto Co., Ltd.) was prepared using the resulting material as an intermediate adhesive layer. The die temperature of the coextrusion molding equipment is 210℃,
The thickness of the sheet is HIPS/adhesive layer/ABS resin =
It is 14/1/4. The interlaminar strength of this laminated sheet was measured using a tensile tester. Display the results -
6. Comparative Example 7 Measurement of the interlaminar strength of a three-layer coextruded laminate sheet produced by the method of Example 7 using ethylene/vinyl acetate copolymer resin (MI 12.0, density 0.948, vinyl acetate content 20% by weight) as the adhesive layer. did. Display the results -
6.

【table】

Claims (1)

[Claims] 1. A polystyrene resin layer and (a) modified ethylene/vinyl acetate copolymer resin obtained by the following modification method.
A polystyrene resin laminate comprising at least two layers: 100 to 10 parts by weight and (b) an adhesive resin layer comprising 0 to 90 parts by weight of an ethylene/vinyl acetate copolymer resin. Modification method: 100 parts by weight of ethylene/vinyl acetate copolymer resin particles, 5 to 200 parts by weight of aromatic vinyl monomer, and a decomposition temperature of 50 to 50 to obtain a half-life of 10 hours.
An aqueous suspension containing 0.01 to 5.0 parts by weight of a radical polymerization initiator per 100 parts by weight of aromatic vinyl monomer at 130°C is heated under conditions that substantially do not cause decomposition of the radical polymerization initiator. After impregnating the ethylene/vinyl acetate copolymer resin particles with aromatic vinyl monomer until the amount of free aromatic vinyl monomer becomes less than 20% by weight, the temperature of this aqueous suspension is raised to 50 to 130°C. The polymerization of the aromatic vinyl monomer is completed to obtain a modified ethylene/vinyl acetate copolymer resin. 2 Polystyrene resin layer and (a) modified ethylene/vinyl acetate copolymer resin obtained by the following modification method
100 to 10 parts by weight and (b) 0 to 90 parts by weight of ethylene/vinyl acetate copolymer resin and a total of 100 parts by weight of these two components, (c) inelastic polymer block A consisting of an aromatic vinyl compound and Consisting of an elastic polymer block B of conjugated diolefin,
(A-B) _o+1 , B-(A-B) _o or A-(B-
_A ) A polystyrene-based material consisting of at least two layers: a thermoplastic block elastic body exhibiting a block structure of o (where n is an integer of 1 to 20) and an adhesive resin layer consisting of 1 to 150 parts by weight. Resin laminate. Modification method: 100 parts by weight of ethylene/vinyl acetate copolymer resin particles, 5 to 200 parts by weight of aromatic vinyl monomer, and a decomposition temperature of 50 to 50 to obtain a half-life of 10 hours.
An aqueous suspension containing 0.01 to 5.0 parts by weight of a radical polymerization initiator per 100 parts by weight of aromatic vinyl monomer at 130°C is heated under conditions that substantially do not cause decomposition of the radical polymerization initiator. After impregnating the ethylene/vinyl acetate copolymer resin particles with aromatic vinyl monomer until the amount of free aromatic vinyl monomer becomes less than 20% by weight, the temperature of this aqueous suspension is raised to 50 to 130°C. The polymerization of the aromatic vinyl monomer is completed to obtain a modified ethylene/vinyl acetate copolymer resin.