JPH021017B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides strong interlayer adhesion using a styrene resin layer and a saponified ethylene-vinyl acetate copolymer layer as main compositions, and improves gas barrier properties, impact resistance, and moldability. This invention relates to a composite sheet with excellent properties. Conventionally, styrenic resins have excellent thermoformability,
It has impact resistance, hygiene, etc., and is relatively inexpensive.
It is widely used as a thermoplastic resin, mainly for food packaging. However, this resin has poor barrier properties against oxygen, carbon dioxide, etc., and is not necessarily sufficient for use in food packaging that is easily affected by oxidation and for long-term storage purposes. On the other hand, vinylidene chloride, saponified ethylene-vinyl acetate copolymer, and polyamide are widely known as resin materials with excellent gas barrier properties. Shows barrier properties. In order to take advantage of this gas barrier property, attempts have been made to combine styrene resin and saponified ethylene-vinyl acetate copolymer to compensate for the drawbacks of styrene resin. Methods for obtaining this composite laminate include a dry lamination method in which one film is coated with a thermosetting adhesive such as urethane and then pressed together with heat, and the two resins are placed in an extruder.
A coextrusion method that obtains a laminated composite sheet from a single die may be considered. Moreover, the industrially best lamination method is the coextrusion method. However, since these two resins have almost no affinity for each other, they cannot be bonded together simply by heat fusion. As one of the means to solve this problem,
-57582 and JP-A-57-63252, etc. are disclosed. The former specification states that the adhesive layer contains a block copolymer (A) consisting of a conjugated diolefin and a monovinyl-substituted aromatic compound, and one or two units of vinyl alcohol, unsaturated carboxylic acid, and derivatives thereof in the molecule. It is described that a resin containing at least one olefin copolymer (B) in a weight ratio of A/B = 10/90 to 90/10 is used. In addition, the latter specification states that the adhesive layer is two layers, a layer containing an isoprene-styrene copolymer on the polystyrene layer side, and a layer containing a graft-modified polyolefin on the saponified ethylene-vinyl acetate copolymer layer side. It is described that an adhesive layer consisting of However, in the adhesive layer of JP-A No. 54-57582,
Adhesion to impact-resistant styrene resins is weak and not necessarily satisfactory, and cannot be put to practical use, particularly when the amount of the block copolymer consisting of a conjugated diolefin and a monovinyl-substituted aromatic compound is small. Furthermore, the adhesive layer disclosed in JP-A-57-63252 has the disadvantage that the extrusion of the block copolymer is unstable, and since there are two adhesive layers, the equipment is complicated and the cost is high. The present invention solves these drawbacks,
The adhesive surface between at least two sheets of styrene resin and saponified ethylene-vinyl acetate copolymer is made of a block polymer with a conjugated diolefin content of 55 to 90% by weight and a vinyl aromatic compound content of 45 to 10% by weight. and a mixture of an olefin copolymer containing at least one of an organic acid, an organic acid anhydride, and a derivative thereof as an adhesive layer, and a block polymer of a conjugated diolefin and a vinyl aromatic compound in a styrene resin. By containing, both the styrene resin layer and the saponified ethylene-vinyl acetate copolymer layer have a high adhesive strength,
Furthermore, the present invention provides a composite sheet that does not require separating the adhesive layer into two layers, has excellent extrusion stability, and has excellent gas barrier properties, impact resistance, and moldability. That is, the present invention provides an adhesive surface between at least two sheets of a styrene resin and a saponified ethylene-vinyl acetate copolymer having a degree of saponification of 70 mol% or more, with a conjugated diolefin content of 55 to 90% by weight and a vinyl aromatic material. A block copolymer (A) with a group compound content of 45 to 10% by weight and an olefinic copolymer (B) containing at least one of organic acids, organic acid anhydrides, and derivatives thereof98 It is characterized by comprising an adhesive layer consisting of a mixed composition of ~70% by weight, and containing a block copolymer consisting of a conjugated diolefin and a vinyl aromatic compound in the styrene resin. The styrenic resin used in the present invention is selected from general transparent styrene resins, styrene-butadiene graft copolymer resins, and mixtures thereof. In addition, saponified ethylene-vinyl acetate copolymer usually has a low vinyl acetate content.
If the content is 50 to 80 mol% and the degree of saponification is 70 mol% or more, it has gas barrier properties, and those within these ranges are preferred. Next, the adhesive layer of the composite sheet used in the present invention is made of a block copolymer (A) consisting of a conjugated diolefin and a vinyl aromatic compound, and an olefin containing at least one of an organic acid, an organic acid anhydride, and a derivative thereof. This is a mixed composition with the copolymer (B). The conjugated diolefin of the block copolymer (A) includes 1,
3-butadiene, 1,3-pentadiene, etc., and vinyl aromatic compounds include styrene, α
-Methylstyrene, vinylbenzene, etc. The composition ratio of these conjugated diolefins is 55~
90% by weight, preferably 60-80% by weight. If the amount of conjugated diolefin is less than 55% by weight, the adhesion to the styrene resin will be weak, and if it exceeds 90% by weight, the adhesiveness will increase and the extrusion stability will deteriorate. Representative examples of this block copolymer (A) include:
These include styrene-butadiene block copolymers, styrene-isoprene block copolymers, etc., and styrene-butadiene block copolymers are preferred. In addition, the olefin copolymer (B) is an olefin copolymer modified with an organic acid, an organic acid anhydride, or a derivative thereof. It is a resin introduced by means. As the ethylenically unsaturated carboxylic acid or its anhydride, acrylic acid,
These include methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, etc., and the copolymerization composition is preferably between 0.1 and 20% by weight.
Furthermore, examples of olefin polymers include polyethylene, polypropylene, ethylene-vinyl acetate copolymers, and copolymers thereof. Next, the olefin polymer modified with organic acid, organic acid anhydride, and their derivatives can be mixed freely, and is determined by the thermoformability of the final composite sheet, and is usually mixed with melt-flow polymers. 12g/10 minutes to 0.1g/10 minutes at 200℃ and 5Kg load is preferable.
If it exceeds 12g/10 minutes, uneven stretching of the sheet will become noticeable during molding, and the product value will be significantly impaired. Examples of the mixture include a modified olefin polymer mainly composed of polypropylene and an olefin polymer modified with an ethylene-vinyl acetate copolymer. The block copolymer (A) in the mixture of the block copolymer (A) and the olefinic copolymer (B) of the adhesive layer of the present invention is 2 to 30% by weight, preferably 2 to 20% by weight. It is. If it is less than 2% by weight, the mixing ratio will not be uniform and the adhesive strength with the styrene resin layer will decrease or vary, and if it exceeds 30% by weight, the thermal stability of the block copolymer (A) itself will decrease. It is not necessary because the extrusion processability is poor due to the lack of adhesiveness and the adhesion does not improve even if the mixing amount is increased. Next, it is essential that the styrenic resin layer of the present invention contains a block copolymer composed of a conjugated diolefin and a vinyl aromatic compound. What is conjugated diolefin of block copolymer?
1,3-butadiene, 1,3-pentadiene, etc., and vinyl aromatic compounds include styrene,
α-styrene, vinyltoluene, etc. Typical examples include styrene-butadiene block copolymers, styrene-isoprene block copolymers, etc., with styrene-butadiene block copolymers being preferred. The block copolymer mixed in the styrenic resin must contain more than 50% by weight of conjugated diolefin and
For rubbery block copolymers containing up to 90% by weight, the amount added is preferably in the range of 5 to 20% by weight. If it is less than 5% by weight, the adhesive strength with the adhesive layer will be weak, and if it exceeds 20% by weight, the entire composite sheet will become flexible and the shape of the container will be weak, making it impractical. Furthermore, in the case of a resinous block copolymer in which the amount of conjugated diolefin in the block copolymer is from 50% by weight or less to about 5% by weight, the amount added is 5 to 5% by weight.
A sufficient adhesion effect with the adhesive layer can be achieved in the range of 100% by weight, and when the amount of conjugated diolefin in the block copolymer is 5 to 20% by weight, it is possible to form a composite without mixing with other styrenic resins. It has a function as a sheet. The composite sheet of the present invention has a structure in which a styrene resin is laminated on one or both sides of a saponified ethylene-vinyl acetate copolymer via an adhesive layer, and a multi-layer structure in which styrene resin is laminated on one or both sides of a saponified ethylene-vinyl acetate copolymer. It may be a composite sheet in which different resins, paper, aluminum foil, etc. are laminated on one side of the saponified material. Next, each layer of this composite sheet contains plasticizers, lubricants, tackifiers, antioxidants,
Stabilizers, colorants, etc. can also be added. The method for manufacturing the composite sheet of the present invention includes: 1) A coextrusion method in which a plurality of extruders are used, each resin is charged into each extruder, and a laminated sheet is extruded from one die. 2) An extrusion lamination method in which some sheets are extruded in advance and laminated using molten resin extruded from an extruder. 3) A lamination method in which all layers are extruded in advance to form a sheet or film and then heated and laminated using hot rolls. is typical. As explained above, the composite sheet obtained by the present invention has extremely good adhesion between resin layers, and has excellent physical properties such as gas barrier properties, thermoformability, and impact resistance for food packaging. It is ideal as a material for containers. This will be explained in detail below using examples. Example: Styrenic resin/adhesive layer resin/
A five-layer sheet of saponified ethylene-vinyl acetate copolymer/adhesive layer resin/styrene resin was extruded using the resins and proportions shown in the table. The total thickness of the composite sheet is 800μ, and the thickness of the styrene resin is
The adhesive resin thickness was set to 10μ, and the saponified ethylene-vinyl acetate copolymer thickness was set to 40μ. The extrudability of each resin was stable and the adhesiveness was also good. The adhesive strength between each layer is shown in the table. Comparative Examples The styrene resins of Comparative Examples 1 to 3 and 5 had poor adhesion when HI was used alone, and the adhesion was also poor when AD was used alone as the adhesive. The symbols and moldability indications in the table are as follows. HI...Impact-resistant styrene resin, Denki Kagaku Kogyo Co., Ltd.
Product name “Dencastyrol HI-E-4” SB1…Styrene-butadiene block copolymer (butadiene content 60% by weight), Denki Kagaku Kogyo Co., Ltd.
Product name “Denka STR1602” SB2…Styrene-butadiene block copolymer (butadiene content 25% by weight) Denki Kagaku Kogyo Co., Ltd.
Product name: “Denka Clearene 730L” AD1…Maleic anhydride modified ethylene-vinyl acetate copolymer, Mitsubishi Yuka Co., Ltd. Product name: “Modetsuku E-”
200H” AD2…Maleic anhydride modified polypropylene Mitsubishi Yuka Co., Ltd., product name “Modetsuku P-300F” EVAL…Saponified ethylene-vinyl acetate copolymer, Kuraray Co., Ltd. product name “EVAL F” GP…General transparent Styrene resin, Denki Kagaku Kogyo Co., Ltd.
Product name “Dencastyrol GP-1” MFI…Melt flow index, JIS-K6870
200°C, 5 kg Adhesive strength...The peel strength between each adhesive layer was measured, and the adhesive strength of the composite sheet was determined by the adhesive layer that was first peeled off. Therefore, the adhesive strength of other adhesive layers is expressed as being higher than that. Formability: 120 x 120 mm using a single-shot vacuum forming machine,
A box-shaped molded product with a depth of 100 mm was molded, and those with a good appearance were rated ○, and those with slight unevenness in sheet elongation on the surface were rated △. 【table】

Claims (1)

[Claims] 1. The adhesive surface between at least two sheets of styrene resin and saponified ethylene-vinyl acetate copolymer with a degree of saponification of 70 mol% or more is bonded to a conjugated diolefin containing 55 to 90% by weight and a vinyl aromatic compound content. Block copolymer (A)2 consisting of 45 to 10% by weight
Olefin copolymer containing ~30% by weight and at least one of an organic acid, an organic acid anhydride, and a derivative thereof
(B) A composite comprising an adhesive layer consisting of a mixed composition of 98 to 70% by weight, and containing a block copolymer consisting of a conjugated diolefin and a vinyl aromatic compound in the styrene resin. sheet.