JPH06184253A - Container for low-temperature storage - Google Patents

Abstract

PURPOSE:To obtain a container excellent in hardness, stiffness, impact resistance and transparency at low temperature and useful as a container, etc., for storing fresh foods. CONSTITUTION:This container is obtained by molding a block copolymer consisting of (A) a polymer block A consisting essentially of two or more vinyl aromatic hydrocarbons and (B) a polymer block B consisting essentially of one or more conjugated dienes having -70 to -20 deg.C Tg value and having 65-85wt.% of the vinyl aromatic hydrocarbon content and >75% block ratio of the vinyl aromatic hydrocarbon block.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses a specific block copolymer to have hardness and rigidity during general handling at room temperature, is transparent, and is excellent in impact resistance at low temperature for low temperature storage. The present invention relates to a container, and is utilized as a container for fresh food or the like that requires freezing or refrigeration by making the best use of its characteristics.

[0002]

2. Description of the Related Art Conventionally, block copolymer resins composed of vinyl aromatic hydrocarbons and conjugated dienes can be easily molded by extrusion molding, injection molding, blow molding, vacuum molding and the like. It is used in a wide range of applications as a material for electrical parts and industrial products. However, these block copolymer resins cannot balance the hardness, rigidity and impact resistance at room temperature depending on the application, and often the impact resistance at low temperature cannot be satisfied. Therefore, various methods have been tried for the purpose of these improvements. For example, Japanese Patent Publication Sho-53-41
No. 7 discloses that a tapered styrene / butadiene block copolymer having a specific taper gradient in the block copolymer chain is blended with polystyrene to obtain a resin composition having excellent transparency and impact resistance. In the examples of JP-B-52-16496, a styrene-butadiene block having a styrene-butadiene copolymer part in which styrene and butadiene are bonded in a fixed ratio in the block copolymer chain. A resin composition has been disclosed in which a copolymer is blended with a rubber-modified polystyrene and which is excellent in impact resistance, fin characteristics and the like. Furthermore, Japanese Examined Japanese Patent Publication No. 62-47
No. 219, a styrene / butadiene block copolymer having a specific amount of a vinyl aromatic hydrocarbon compound block homopolymer segment in a block copolymer chain is blended with a thermoplastic resin to improve impact resistance and impact resistance. A resin composition having excellent low temperature characteristics is disclosed.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a container for low temperature storage which is excellent in hardness and rigidity at room temperature, is transparent, and has sufficient impact resistance at low temperature.

[0004]

That is, the present invention is
A polymer block A containing at least two vinyl aromatic hydrocarbons as a main component and a polymer block B containing at least one conjugated diene as a main component, and the Tg value of the block B is in the range of -70 ° C to -20 ° C. And a container for low-temperature storage formed by molding a block copolymer having a vinyl aromatic hydrocarbon content of 65% by weight or more and 85% by weight or less and a block ratio of the vinyl aromatic hydrocarbon block of more than 75% by weight. .

The present invention will be described in detail below. The block copolymer used in the present invention is a block copolymer having at least two vinyl aromatic hydrocarbon-based polymer blocks A and at least one conjugated diene-based polymer block B. is there. Here, the polymer block A mainly composed of vinyl aromatic hydrocarbon is a polymer block having a vinyl aromatic hydrocarbon content of 70% by weight or more, preferably 80% by weight or more. Further, the polymer block B mainly composed of a conjugated diene has a Tg value of -70 ° C to -2.
The content of the conjugated diene can be set within the range of 0 ° C. When a random copolymer portion of a vinyl aromatic hydrocarbon and a conjugated diene is present in the polymer block A mainly containing the vinyl aromatic hydrocarbon or the polymer block B mainly containing the conjugated diene, they are copolymerized. The vinyl aromatic hydrocarbon present may be distributed uniformly in the polymer block or may be distributed in a taper (gradual decrease) form. The block copolymer used in the present invention can be basically produced by a conventionally known method. For example, JP-B-36-19286, JP-B-43-17979, JP-B-48-2423 and JP-B-49- No. 36957, Japanese Patent Publication No. 57-49
The methods described in Japanese Patent Publication No. 567, Japanese Patent Publication No. 58-11446 and the like can be mentioned, but the production conditions of each constituent polymer must be set so as to satisfy the requirements described later. All of the above known methods are methods of block copolymerizing a conjugated diene and a vinyl aromatic hydrocarbon in an hydrocarbon solvent using an anionic initiator such as an organic lithium compound.

The polymer structure of the block copolymer used in the present invention is, for example, A- (BA) _n , A- (BA) _n -B, B- (A-
B) _{n + 1} , (In the above formula, A is a polymer block mainly containing vinyl aromatic hydrocarbons, and B is a polymer block mainly containing a conjugated diene. Boundary between A block and B block Do not necessarily have to be clearly distinguished. N is an integer of 1 or more, generally 1 to 5.), or a linear block copolymer represented by the general formula: [(AB) _k ] _{m + 2-} X, [(AB) _k- A]
_{m + 2-} X [(B-A) _k ] _{m + 2-} X, [(B-A) _k- B]
_{m + 2-} X (In the above formula, A and B are the same as above, and k and m
Is an integer of 1 or more, generally 1 to 5. X represents a residue of a coupling agent such as silicon tetrachloride or tin tetrachloride or a residue of an initiator such as a polyfunctional organolithium compound. ), A radial block copolymer represented by the formula (1), or a mixture of any of these block copolymers having a polymer structure can be used.

The vinyl aromatic hydrocarbon used in the present invention is styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinyl. Although there are anthracene, 1,1-diphenylethylene and the like, styrene is particularly common. These may be used alone or in combination of two or more.

The conjugated diene is a diolefin having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene),
2,3-Dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and the like, and particularly common ones include 1,3-butadiene and isoprene. These may be used alone or in combination of two or more.

The preferred range of the vinyl aromatic hydrocarbon content of the block copolymer used in the present invention is 65% by weight or more and 85% by weight or less, more preferably 70% by weight.
It is above 80% by weight. If the vinyl aromatic hydrocarbon content of the block copolymer is less than 65% by weight, the hardness and rigidity at room temperature will be poor, and conversely if it exceeds 85% by weight, impact resistance will decrease, which is not preferable.

The Tg value of the polymer block B of the block copolymer of the present invention is preferably in the range of -70 ° C to -20 ° C, more preferably -60 ° C to -30 ° C. This T
When the value is out of the range of g value, low temperature characteristics, particularly low temperature impact resistance, are unfavorable. The Tg value referred to herein was measured by a viscoelasticity measuring device, for example, 983 DMA manufactured by DuPont. It is the temperature obtained from the top temperature of the tan δ peak of dynamic viscoelasticity. The Tg value of the block B can be easily changed by, for example, the vinyl aromatic hydrocarbon content of the random copolymer portion of the conjugated diene and the vinyl aromatic hydrocarbon.

The low temperature impact resistance temperature of the cryopreservation container of the present invention means that the temperature for maintaining the impact resistance is -10 ° C or lower. The block ratio of the vinyl aromatic hydrocarbon block of the block copolymer used in the present invention needs to exceed 75% by weight. When the block rate is 75% by weight or less, the rigidity and the low temperature impact resistance are poor, which is not preferable. The block ratio of the vinyl aromatic hydrocarbon block is the weight and weight ratio of the vinyl aromatic hydrocarbon and the conjugated diene in the step of copolymerizing at least a part of the vinyl aromatic hydrocarbon and the conjugated diene during the production of the block copolymer. It can be controlled by changing the polymerization reactivity ratio and the like. As a specific method, (a) a mixture of a vinyl aromatic hydrocarbon and a conjugated diene is continuously supplied to a polymerization system for polymerization. And / or (b) a method of copolymerizing a vinyl aromatic hydrocarbon and a conjugated diene using a polar compound or a randomizing agent can be adopted.

Examples of polar compounds and randomizers include ethers such as tetrahydrofuran, diethylene glycol dimethyl ether and diethylene glycol dibutyl ether, amines such as triethylamine and tetramethylethylenediamine, thioethers, phosphines, phosphoramides, alkylbenzene sulfonates, potassium salts. And sodium alkoxide.

In the present invention, the block ratio of the vinyl aromatic hydrocarbon polymer block incorporated in the block copolymer is the di-catalyzed amount using osmium tetroxide as a catalyst.
A method of oxidatively decomposing a block copolymer with tertiary butyl hydroperoxide (IM KOLTH
OFF, et al. J. Polym. Sci. 1,4
29 (1946)), which is a vinyl aromatic hydrocarbon polymer block component (provided that the average degree of polymerization is about 3).
The vinyl aromatic hydrocarbon polymer component of 0 or less is excluded), and the block ratio (% by weight) is the vinyl aromatic hydrocarbon weight in the weight of all the vinyl aromatic hydrocarbons in the block copolymer. It is the weight ratio of the united block.

The molecular weight of the block copolymer used in the present invention can be optionally adjusted by the amount of the catalyst used for polymerization, but from the viewpoint of moldability, the melt flow index (JIS
Measured by K-6870. Condition is G condition and temperature is 200
C., weight 5 kg) is 0.1 to 100 g / 10 min, preferably 1 to 50 g / 10 min. If desired, the block copolymer used in the present invention can be hydrogenated in the presence of a hydrogenation catalyst in an inert solvent and used as a hydrogenated product. As a concrete method, Japanese Patent Publication No. 42-870.
The method described in JP-B No. 4 and JP-B No. 43-6636, and particularly preferably the method described in JP-B-63-4841 and JP-B-63-5401.

The block polymer used in the present invention may contain any styrene-based copolymer or an additive, if necessary. The type of styrene copolymer is ABS resin,
AES resin, AAS resin, AS resin, polystyrene resin, impact-resistant polystyrene resin and the like, and the kind of the additive is not particularly limited as long as it is generally used for compounding plastics. For example, glass fiber, Inorganic reinforcing agent such as glass beads, silica, calcium carbonate, talc, organic fiber, organic reinforcing agent such as coumarone indene resin, cross-linking agent such as organic peroxide, inorganic peroxide, titanium white,
Carbon black, pigments such as iron oxide, dyes, flame retardants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers,
Other extenders or mixtures thereof may be mentioned.

The cryopreservation container of the present invention can be molded by the same processing means as a usual thermoplastic resin, and can be used for any application requiring low temperature characteristics of the container.
For example, it can be used for containers of OA equipment parts, daily necessities, foods, miscellaneous goods, light electric parts, etc. by injection molding, blow molding, etc. In addition, it can be used for a wide range of applications such as food containers, fruits and vegetables, confectionery containers and the like, which are obtained by thermoforming extruded products such as sheets and films by a method such as vacuum forming and pressure forming.

[0017]

Example 1 After the autoclave was internally replaced with nitrogen gas, 50 kg of purified and dried cyclohexane was charged,
Then, the mixture was stirred and heated to 75 ° C. Next, n-butyllithium was added as a catalyst. The amount of addition is M.M. of the block copolymer. It was adjusted so that I was the predetermined value shown in Table 1. Then, purified and dried butadiene and / or styrene monomer was added by a plunger pump in an amount of 10 Kg of the total amount of the monomer at a monomer composition ratio shown in Table 1 to continue the polymerization. The monomer supply time was 40 minutes for A1, 90 minutes for B1, and 40 minutes for A2. After the completion of the polymerization in a predetermined polymerization step, 20 ml of methanol was added to stop the polymerization, 100 g of 4-methyl-2,6-di-tert-butylphenol as an antioxidant was further added, and the solvent was removed using a double drum dryer. . After pelletizing the block copolymer with an extruder, a J-200SB injection molding machine manufactured by Japan Steel Works, Ltd. was used to measure length × width × height (thickness) of 200 mm × 150 mm × 50 mm.
A rectangular parallelepiped box (1.5 mm) was molded. Next, in order to measure the physical properties of the molded product, the test piece was cut as necessary. Table 1 shows the analytical values of the obtained block copolymer and the physical properties of the injection-molded products.

[0018]

[Table 1]

The notes in Table 1 are as follows. (Note-1) A is a polystyrene block, and B is a polybutadiene or a copolymer block of polybutadiene and polystyrene. Si is the residue of the coupling agent Sicl ₄ . (A1-B1) ₂ structure -A2 After polymerizing repeated twice (A1-B1), is obtained by polymerizing A2. (Note-2) JIS K6870 (200 ° C, load 5K
Compliant with g). (Note-3) Tan δ peak temperature of dynamic viscoelasticity by 983 DMA manufactured by Dupont. (Note-4) According to JIS K5400. (Note-5) Compliant with ASTM D790 (Kgf / c
m ² ). (Note-6) Compliant with ASTM D1709 (Kgf · c
m). (Note-7) After packing 500 g of clay in the molded product box and closing the lid, the product was kept in a freezer at -30 ° C for 24 hours, then taken out, and quickly taken from a height of 1 m on a steel plate with a thickness of 20 mm to 30 mm. The pieces were dropped and judged by the number of pieces damaged.

[0020]

The block copolymer within the scope of the present invention was a transparent molded article having excellent rigidity and impact resistance at room temperature and good low temperature impact strength.

[0022]

Examples 2 to 4 and Comparative Examples 1 to 4 After autoclaving the interior of the autoclave with nitrogen gas, 50 kg of purified and dried cyclohexane was charged, and then the mixture was stirred and heated to 75 ° C. Next, n-butyllithium was added as a catalyst. The amount of addition is M.M. of the block copolymer. It was adjusted so that I was the predetermined value shown in Table 1. Then, purified and dried butadiene and / or styrene monomer was added by a plunger pump in an amount of 10 kg of the total amount of monomer under the conditions shown in Table 1 to continue the polymerization. The monomer was supplied at the same supply rate as in Example 1. Further, the addition of the antioxidant after the completion of the polymerization, pelletization, molding and the like were performed in the same manner as in Example 1. The physical properties of the obtained injection-molded product are shown in Table 1.

[0023]

Examples 5 and 6 The block copolymer and polystyrene (Asahi Kasei Polystyrene 666 manufactured by Asahi Kasei Corporation) were melt-kneaded and pelletized using an extruder, and molded in the same manner as in Example 1. Table 2 shows the type, compounding composition and injection molding properties of the block copolymer.

[0024]

Example 7 Using the composition of Example 5, a thickness of 0.3 mm
An extruded sheet of was prepared. Then, a cylindrical cup having an inner volume of 200 mm was formed from this extruded sheet by vacuum forming. Example 1 except that 150 g of sand was placed in this cup
The low temperature impact strength was measured by the same method. As a result, the number of breakages was as small as 5, showing a good result.

[0025]

[Table 2]

[0026]

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to obtain an unprecedented transparent container which maintains hardness and rigidity at room temperature and has improved impact resistance at low temperature. By utilizing this characteristic, a container for low temperature preservation suitable for a container for storing fresh foods by injection molding or a container for frozen dessert by extrusion molding is provided.

Claims (1)

[Claims] 1. A polymer block A containing at least two vinyl aromatic hydrocarbons as a main component and a polymer block B containing at least one conjugated diene as a main component, and the block B has a Tg value of -70 ° C. or more. Within the range of -20 ° C, the vinyl aromatic hydrocarbon content is 65% by weight or more and 85% by weight or more.
Below, the block ratio of the vinyl aromatic hydrocarbon block is 7
A low-temperature storage container formed by molding a block copolymer in excess of 5% by weight.