JPS6221037B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention can easily provide an adhesive resin composition particularly suitable for manufacturing multilayer composite molded articles by melt adhesion, especially a laminate of a polyolefin synthetic resin and a polymer that has conventionally been difficult to bond to a polyolefin synthetic resin. The present invention relates to a novel adhesive resin composition. In general, polyolefin-based synthetic resins have established a wide range of uses due to their moldability, mechanical properties, water resistance, chemical resistance, etc. However, it is inferior in gloss, surface scratchability, and decorative properties such as coloring, and has poor weather resistance.
It is difficult to say that the oil resistance is also sufficient. Furthermore, when used as a food packaging material, it has a drawback that it has high permeability to gases such as oxygen and carbon dioxide, and food cannot be stored for a long period of time. A possible method to compensate for these drawbacks is to laminate the polyolefin synthetic resin with other materials having different properties. For example, laminates such as polyethylene/nylon, polyethylene/polystyrene, polypropylene/polyvinyl chloride, polyethylene/polymethyl methacrylate, and polyethylene/ethylene-vinyl acetate copolymer saline compounds can be considered. However, there is no adhesion between such dissimilar materials, and such laminated structures very easily cause delamination. Therefore, in order to improve this adhesion, methods such as applying an adhesive after applying special treatment to the surface of the film to be bonded have been adopted, but this requires a great deal of time and effort. I don't like it. On the other hand, with advances in coextrusion technology, it has become common to coextrude laminates of three or more layers, using carboxylated modified polyolefin as an adhesive layer. However, even in this method, the material to be laminated with polyolefin is nylon or ethylene.
Although we have had success with products that bind to carboxylated modified polyolefins, such as saponified vinyl acetate copolymers, we have succeeded in developing products that are inert to carboxylated modified polyolefins such as polyesters, styrene resins, and acrylic resins. Polymers had no effect. In order to laminate such an inert polymer with a non-polar, inert polyolefin, there was no choice but to use an extremely adhesive resin or elastomer, but such a method did not provide sufficient adhesion. In addition, heat resistance and coextrusion moldability were poor, and it was difficult to maintain a high level of product value such as appearance and colorability. In particular, the tendency for the adhesive strength between layers of laminated materials to decrease due to penetration of water or chemicals has limited their use as food packaging materials. However, the present inventors have completed the present invention as a result of extensive research into adhesive polymers that can significantly improve adhesive strength and maintain coextrusion moldability and product value at a high level. That is, the present invention provides a composition comprising a block copolymer shown below comprising a monovinyl-substituted aromatic compound and a conjugated diene, and an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 to 50% by weight. The present invention provides a novel adhesive resin composition in which an unsaturated carboxylic acid or an acid anhydride thereof is graft-modified. The block copolymer consisting of a monovinyl-substituted aromatic compound and a conjugated diene, which is a component of the composition of the present invention, is substantially represented by the following general formula, has a molecular weight of 10,000 to 500,000, and has a conjugated diolefin content of 10 ~90% by weight. (A-B)n, A-(B-A)n, B-(A-B)n, (A-B)mX, where A is a polymer block consisting essentially of a vinyl-substituted aromatic compound; is a polymer block consisting essentially of conjugated diolefin, n is an integer of 1 to 10, X is a polyfunctional compound to which m polymer chains can be bonded, and m is an integer of 3 to 7. The block copolymer represented by the above general formula is a thermoplastic elastomer that has physical properties equivalent to vulcanized rubber at room temperature and exhibits plasticity similar to ordinary thermoplastic plastics when heated. Therefore, the block represented by the above general formula does not necessarily need to be composed of exactly the same monomer, but may be any one that can be a thermoplastic elastomer. Therefore, it is sufficient that it is substantially block-shaped. As the conjugated diolefin which is one component of the block copolymer used in carrying out the present invention, 1,3-butadiene and isoprene are most preferred, and in addition, 1,3-pentadiene, 2,3-dimethylbutadiene, and is a mixture of two or more of these. Furthermore, as the monovinyl-substituted aromatic compound, styrene is most preferable, and o-, m-, p-
- Vinyl toluene, vinyl xylene, ethyl styrene, isopropylstyrene, ethyl vinyl toluene, tertiary butyl styrene, diethyl styrene, vinyl naphthalene, etc. or two of these
It is a mixture of more than one species. The block copolymer represented by the above general formula is produced by a solution polymerization method using a lithium-based catalyst in an inert medium. In general, the polymerization mode when conjugated diolefins or (and) monovinyl-substituted aromatic compounds are polymerized using a lithium-based catalyst is called "living polymerization," and a large amount of polymerization occurs during or after the polymerization. The partial polymer has lithium added to the end of the molecule and is an active polymer molecule that still has polymerization ability. Therefore, for example, if a conjugated diolefin is polymerized using a lithium-based catalyst and then a monovinyl-substituted aromatic compound is added, a block copolymer in which a monovinyl-substituted aromatic compound polymer is added to a conjugated diolefin polymer is formed. A conjugated diolefin polymer block or (and) a monovinyl-substituted aromatic compound polymer block is added to these block copolymers by carrying out similar operations to obtain the above general formula (A-B)n. A block copolymer can be produced. Alternatively, for example, using a lithium-based catalyst, a monovinyl-substituted aromatic compound is first polymerized, then a conjugated diolefin is added and polymerized, and then a monovinyl-substituted aromatic compound is polymerized to form a monovinyl-substituted aromatic compound. A block copolymer in which compound polymer block - conjugated diolefin polymer block - monovinyl-substituted aromatic compound polymer block is connected can be produced, and by further performing the same operation, a conjugated diolefin polymer can be added to these block copolymers. block and monovinyl-substituted aromatic compound polymer block are added to form the above general formula A-(B-A).
n block copolymers can be produced. Furthermore, in general, when a conjugated diolefin and a monovinyl-substituted aromatic compound are polymerized together in an inert solvent such as hexane or benzene using a lithium-based catalyst, the polymerization rate of the conjugated diolefin is lower than that of the monovinyl-substituted aromatic compound. The polymerization rate is significantly higher than the polymerization rate of the compound, and most of the monovinyl-substituted aromatic compound is polymerized after most of the conjugated diolefin has been polymerized. ,
Even when polymerized using a lithium-based catalyst and further polymerized by adding a mixture of a conjugated diolefin and a monovinyl-substituted aromatic compound, the conjugated diolefin polymer and the monovinyl-substituted aromatic compound were added alternately.
Block copolymers can be made. Furthermore, in the present invention, the monovinyl-substituted aromatic compound is first polymerized in the presence of a lithium-based catalyst to form a block polymer of the polymonovinyl-substituted aromatic compound, and then the conjugated diene is added. A polymonovinyl substituted aromatic compound-polyconjugated diene block copolymer is prepared and this block copolymer with terminal lithium is reacted with a polyfunctional compound having at least three reactive groups that react with the terminal lithium. As a result, a block copolymer having the general formula (A-B)nX can be produced. The content of conjugated diolefin in the block copolymers of the invention is between 10 and 90% by weight, preferably between 30 and 85% by weight. If it is less than the above range, the elasticity will be low and it will become resin-like and the adhesiveness will be reduced, and if it exceeds the above range, the tensile strength will be weak and the adhesiveness will also be reduced. The molecular weight of the block copolymer of the present invention is 10,000 to 500,000, preferably 50,000 to 20,000.
Ten thousand. In the above formula, n is 1 or more, preferably 2 or more, and it is desirable for a thermoplastic elastomer with good adhesiveness to have at least two blocks of A. Moreover, it is preferable that n is 10 or less; if it is 11 or more, a thermoplastic elastomer with high tensile strength and good adhesiveness cannot be obtained. Further, the block copolymer represented by the above general formula can be used by hydrogenating the remaining double bonds by an appropriate method in order to improve its thermal stability and weather resistance. Next, the vinyl acetate content of the ethylene-vinyl acetate copolymer, which is another component of the composition of the present invention, is preferably in the range of 5 to 50% by weight, more preferably 10 to 30% by weight. If it exceeds this range, not only will extrusion molding be difficult, but the adhesive strength will also decrease.
If it is lower than this range, the adhesive force will also be insufficient. In addition, MI of ethylene-vinyl acetate copolymer
By selecting a range of 0.5 to 100, more preferably 1 to 50, adhesiveness and moldability can be maintained at a high level. The blending ratio of the above block copolymer in the resin composition consisting of the above block copolymer and ethylene-vinyl acetate copolymer is 1% to the total composition.
A range of from 1 to 95% by weight, particularly preferably from 1 to 50% by weight is suitable. This blending ratio not only affects the adhesive force itself to various adherends, but also affects the environmental resistance of the adhesive force, especially the chemical resistance. In particular, when the blending ratio of the above block copolymer increases, the adhesive strength to various adherends generally improves, and the water resistance of the adhesive strength also improves, but the oil resistance and organic solvent resistance of the adhesive strength decreases. The heat resistance of the composition is also reduced. Therefore, adhesive polymers for multilayer materials for food packaging applications that require high adhesive strength and high water resistance and oil resistance are recommended.
The blending ratio of the above block copolymer is preferably 1 to 50% by weight. Examples of the unsaturated carboxylic acid or unsaturated carboxylic anhydride to be graft-modified on at least one of the above block copolymer and ethylene-vinyl acetate copolymer include maleic acid, fumaric acid, itaconic acid, acrylic acid, and methacrylic acid. , crotonic acid, maleic anhydride, itaconic anhydride, sorbic acid, cinnamic acid, vinyl acetic acid, etc., and these may be used alone or in combination. In particular, maleic acid and maleic anhydride give favorable results.
The amount of unsaturated carboxylic acid or unsaturated carboxylic anhydride used is 0.01 to 5
It is desirable that the amount is in the range of 0.05 to 3% by weight, and if it exceeds this range, the thermal stability of the modified composition will decrease and molding will become difficult, and if it is less than this range, the adhesion will not be sufficient. Various methods can be employed to graft a monomer consisting of an unsaturated carboxylic acid or an unsaturated carboxylic acid anhydride (hereinafter sometimes referred to as a graft monomer) to the above copolymer composition. One method is to mix the copolymer composition, graft monomer, and radical generator, melt and homogenize the mixture, and react with the copolymer composition. There is a method of adding, mixing, and reacting a graft monomer and a radical generator to a copolymer composition. On the other hand,
It is also possible to employ a method in which one of the copolymers in the copolymer composition is subjected to the above graft modification and then the other copolymer is added and mixed. The method of using the above-mentioned graft-modified composition as a hot-melt adhesive and the selection of the adherend are possible in various cases, but particularly preferred are polyolefin-based synthetic resins, which are useful even though they do not adhere to them. It is used as an intermediate adhesive layer in multilayer composite molding with various thermoplastic resins having such characteristics. The polyolefin-based synthetic resins mentioned here include homopolymers or copolymers of α-olefins such as low-density polyethylene, medium- and high-density polyethylene, crystalline polypropylene, crystalline ethylene-propylene block copolymers, and polybutene. However, ethylene-vinyl acetate copolymers containing ethylene as a main component, ethylene-acrylic ester copolymers, ionomer resins, and the like are also included. It also includes composite resins in which polyolefin synthetic resins are filled with inorganic fillers, glass fibers, wood flour, etc. These can also be used in blends with each other. On the other hand, various thermoplastic resins that have the useful properties mentioned here include:
Examples include acrylic resins, styrene resins, vinyl chloride resins, vinylidene chloride resins, thermoplastic polyester resins, polyamide resins, saponified ethylene-vinyl acetate copolymers, and high nitrile resins. For example, a polyolefin synthetic resin, a polymethyl methacrylate resin, and the graft-modified composition of the present invention as an intermediate adhesive layer are extruded from separate extruders, led to the same coextrusion multilayer die, and formed into various shapes. surface hardness, weather resistance,
It is possible to obtain a multilayer composite molded article that has excellent impact resistance, economic efficiency, good delamination resistance, little generation of gel-like substances, and high product value. By changing the structure and molding method of this multilayer die, a multilayer composite inflation film,
It is possible to produce multilayer composite T-die films or sheets, multilayer composite pipes, multilayer composite blow molded products, multilayer composite injection molded products, multilayer composite injection molded products, multilayer composite foam molded products, and the like. Also, polyethylene terephthalate,
It is also possible to obtain biaxially oriented films or sheets of polyamide, polypropylene, etc., and laminates of materials such as cellophane, paper, aluminum foil, polyethylene, polypropylene, ionomers, etc. By using the above graft-modified copolymer composition as the adhesive layer of these laminates, laminates with excellent delamination resistance can be obtained. In this intermediate adhesive layer, it is possible to increase the adhesive strength by mixing a part of the polyolefin resin and/or various thermoplastic resins to be laminated together to improve molding processability.
This is possible as long as it does not reduce product performance. In addition to the above, the adhesive resin composition of the present invention can be applied to various polar substances such as metals such as steel and aluminum, glass, ceramics, celluloses such as paper and wood, leather, and synthetic leather. It can be used for thermal melt bonding with other substances and can exhibit effective adhesive strength. The resin composition of the present invention may optionally contain a heat stabilizer, a lubricant, a thickener, a filler, a coloring agent, etc. in addition to the above-mentioned composition within a range that does not significantly impair adhesive strength and moldability. The present invention will be explained below with reference to Examples. In the examples, peel strength was measured by cutting out a 20 mm x 100 mm test piece, peeling off a portion, and using a tensile tester at a peel angle of 180° and a tensile speed of 50 mm/min. Example 1 (A) Monomer mixture of 1,3-butadiene and styrene in a weight ratio of 50:50 in a nitrogen gas atmosphere
To a 15% by weight n-hexane solution containing 40 parts by weight, 1.25 mmol of n-butyllithium was added as active lithium per 100 g of total monomers and polymerized at 60°C for 4 hours. After most of the monomers have been polymerized, a monomer mixture of 1,3-butadiene and styrene in a weight ratio of 65:35 is added to the active solution.
A 15% by weight n-hexane solution containing 60 parts by weight was added and polymerized at 70°C for 5 hours, and then 0.5 parts by weight of 2,6-dit was added as a stabilizer to this copolymer solution.
- After adding butyl-p-cresol, n-hexane is evaporated and the styrene content is approximately 41% by weight.
A substantially BABA type block copolymer was obtained. The styrene-butadiene block copolymer obtained in (A) and the ethylene-vinyl acetate copolymer with a vinyl acetate content of 20% by weight and an MI of 20 are combined in the proportions shown in Table 1.
100 parts by weight, 1.0 parts by weight of maleic anhydride, and 2,5-dimethyl-2,5-di-t- as a radical generator.
Graft modification was carried out by kneading 0.02 parts by weight of butyl peroxyhexane at 200°C using a twin-screw extruder. This modified copolymer and low-density polyethylene with a density of 0.918 and MI5.0 were heated together at 180°C in separate extruders.
The molten composite film was extruded by feeding it into a multi-manifold two-layer die. The thickness of this composite film is 15μ for the modified copolymer layer and 45μ for the low density polyethylene layer.
It was μ. The modified copolymer side of this molten film has a thickness of 30μ without being anchor coated.
A laminate film was produced by pressure-bonding lamination on a nylon 6 film using a conventional method. The interlayer peel strength of the obtained laminate film after being left in the air, and the interlayer peel strength after immersing the laminate film in water and acetone for 24 hours, respectively, were measured. The results are shown in Table 1. Comparative Example 1 In Example 1, the same procedure as in Example 1 was carried out except that the ethylene-vinyl acetate copolymer used in Example 1 was used alone as the base polymer when producing the modified copolymer composition. After producing a modified resin and molding a laminate, this was evaluated. The results are shown in Table 1. Comparative Example 2 In Example 1, the same procedure as in Example 1 was carried out except that the styrene-butadiene block copolymer obtained in (A) was used alone as the base polymer when producing the modified copolymer composition. After producing a modified resin and molding a laminate, this was evaluated. The results are shown in Table 1. Comparative Example 3 A laminate was produced in the same manner as in Example 1, except that the raw material ethylene-vinyl acetate copolymer alone was used unmodified instead of the modified copolymer composition. After molding, it was evaluated. The results are shown in Table 1. Comparative Example 4 A laminate was produced in the same manner as in Example 1, except that the raw material styrene-butadiene block copolymer alone was used unmodified instead of the modified copolymer composition. After molding, it was evaluated. The results are shown in Table 1. Comparative Example 5 In Example 1, when producing a modified copolymer composition, an ethylene-vinyl acetate copolymer with a vinyl acetate content of 3% by weight and an MI of 5.0 was used instead of the ethylene-vinyl acetate copolymer used in Example 1. A modified resin composition was produced in the same manner as in Example 1 except for using the polymer, and a laminate was molded and then evaluated. The results are shown in Table 1. Comparative Example 6 In Example 1, when producing a modified copolymer composition, an ethylene-vinyl acetate copolymer with a vinyl acetate content of 55% by weight and an MI of 150 was used instead of the ethylene-vinyl acetate copolymer used in Example 1. A modified resin composition was produced in the same manner as in Example 1, except for using coalescence, and a laminate was molded and then evaluated. The results are shown in Table 1.

[Table] Example 2 In Example 1, at the stage of manufacturing the laminate film, instead of using nylon 6 film as the base film, a 12μ thick polyethylene terephthalate film that had not been subjected to anchor coating treatment was used. A laminate film was produced in the same manner as in Example 1. The interlayer peel strength of the obtained laminate film was 7.2 Kg/25 mm, which was good. Example 3 70 parts by weight of the ethylene-vinyl acetate copolymer used in Example 1, 1.0 parts by weight of maleic acid,
Graft-modified pellets were obtained by kneading 0.01 part by weight of 2,5-dimethyl-2,5-di-t-butylperoxyhexane at 200 DEG C. in a twin-screw extruder. This was added to the block copolymer 30 obtained in (A) in Example 1.
Parts by weight were mixed and kneaded again at 180°C using a twin-screw extruder to obtain a modified copolymer composition. This modified copolymer composition was melted at 180°C and supplied to the middle layer of a three-layer composite die of a sheet forming machine. On the other hand, low-density polyethylene with MI2.0 and density 0.919 was heated at 180℃, and high-impact polystyrene (manufactured by Asahi Dow Co., Ltd., product name Styron #475) was heated at 200℃.
The mixture was melted in separate extruders and supplied to both outer layers of the above three-layer composite die heated to 210°C. The dice used were of a multi-manifold type. As a result, a multilayer sheet was obtained with a high impact polystyrene layer of 0.7 mm, a modified copolymer layer of 0.1 mm as an intermediate layer, and a polyethylene layer of 0.2 mm. The interlayer peel strength of this sheet was 4.5 kg/25 mm. Example 4 Using the coextrusion three-layer sheet forming machine used in Example 3, the composition obtained in Example 3 was heated at 180°C.
Inorganic filler-filled reinforced high-density polyethylene (manufactured by Asahi Kasei Corporation, Roimer S1360) with an MI of 0.1 and a density of 1.40.
At 220℃, polymethyl methacrylate resin (molecular weight 200,000, methyl acrylate copolymerization amount 10% by weight) was fed to separate extruders at 210℃ and introduced into a three-layer composite die heated to 220℃. A multilayer sheet was molded in the same manner as in Example 3. The result is an inorganic filler-filled reinforced high-density polyethylene layer.
A multilayer sheet was obtained with a thickness of 0.7 mm, a modified copolymer layer of 0.1 mm as an intermediate layer, and an acrylic resin layer of 0.2 mm. The interlayer peel strength of this sheet was 8.5 kg/25 mm.

Claims (1)

[Scope of Claims] 1. A composition consisting of a block copolymer represented by the following general formula consisting of a monovinyl-substituted aromatic compound and a conjugated diene, and an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 to 50% by weight. An adhesive resin composition in which at least one of the products is graft-modified with an unsaturated carboxylic acid or an acid anhydride thereof. (A-B)n, A-(B-A)n, B-(A-B)n, (A-B)mX (where A is a polymer block consisting essentially of a vinyl-substituted aromatic compound, B is a polymer block consisting essentially of conjugated diolefin, n is an integer from 1 to 10, X is a polyfunctional compound to which m polymer chains can be bonded, and m is an integer from 3 to 7. ). 2. The adhesive resin composition according to claim 1, wherein a copolymer having a vinyl acetate content of 10 to 30% by weight and an MI of 0.5 to 100 is used as the ethylene-vinyl acetate copolymer. 3 Unsaturated carboxylic acid or its acid anhydride is
The adhesive resin composition according to claim 1, which is maleic acid or maleic anhydride. 4. The adhesive resin composition according to claim 1, wherein the proportion of the block copolymer comprising a monovinyl-substituted aromatic compound and a conjugated diene in the composition is 1 to 50% by weight.