JP2612388B2 - Styrene resin sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a styrene-based resin sheet having excellent transparency which shortens the molding cycle in vacuum forming and pressure forming and increases toughness to prevent cracking during trimming of a molded product. .

[0002]

2. Description of the Related Art Conventional polystyrene sheets are light-weight containers for storing foods, stationery, and miscellaneous goods because of their excellent rigidity, transparency, and moldability. It has been heavily used. Polystyrene sheets are thermoformed into various lightweight containers by vacuum forming and air pressure forming machines. Shortening the molding cycle during thermoforming improves productivity, so a styrene resin sheet that can shorten the molding cycle is desired. .

In order to shorten the molding cycle, polystyrene sheets to which an internal plasticizer has been added have been tried, but no significant improvement has been observed. The addition of the internal plasticizer reduces the strength of the polystyrene sheet. Further, at the time of sheet forming or thermoforming, there is a problem that an internal plasticizer is precipitated, thereby lowering productivity and impairing the sheet appearance.

[0004] Since polystyrene is an inherently brittle resin, in order to compensate for this drawback in polystyrene sheets,
Sheet molding is performed using a styrene-based resin in which a rubber-like elastic material, for example, a styrene-butadiene block copolymer is blended with polystyrene. The strength of the styrene-based resin sheet increases as the content of the rubber-like elastic material increases, but the strength in the direction perpendicular to the sheet extrusion direction does not improve, and the bending strength in this direction does not improve.
This often has an adverse effect on the strength of the final molded product, and there is a strong demand for improvement.

[0005]

DISCLOSURE OF THE INVENTION In view of the above situation, the present inventors have made a styrene-based resin containing a resin obtained by copolymerizing a terpene and a vinyl aromatic hydrocarbon in a styrene-based resin and hydrogenating the copolymer. In order to shorten the molding cycle at the time of vacuum forming and pressure forming and to increase the toughness, especially the strength in the direction perpendicular to the sheet extrusion direction, we have studied diligently to develop a highly transparent styrene resin composition sheet. The invention has been reached.

That is, the present invention provides a vinyl aromatic polymer having a styrene polymer (I), at least one vinyl aromatic hydrocarbon polymer block and at least one polymer block mainly composed of a conjugated diene. A resin composition comprising a block copolymer (II) having a weight ratio of a hydrocarbon to a conjugated diene of 60:40 to 95: 5, wherein the styrene-based polymer (I) and the block copolymer (II) Styrene resin 1 having a weight ratio of 99.5: 0.5 to 50:50
Per 100 parts by weight, a resin obtained by copolymerizing a terpene and a vinyl aromatic hydrocarbon and hydrogenating the copolymer is 0.5 to 20 parts by weight.
An object of the present invention is to provide a styrene resin composition sheet excellent in strength and transparency, which is characterized by being formed from a styrene resin composition containing parts by weight. Hereinafter, the present invention will be described in detail.

The styrenic resin referred to in the present invention is a resin composition comprising a styrenic polymer (I) and a block copolymer (II). The styrene-based polymer (I) referred to in the present invention is a polymer obtained by polymerizing a styrene-based monomer alone or a mixture such as styrene, α-methylstyrene, Ptbutylstyrene, and p-methylstyrene; Monomers copolymerizable with styrene monomers, for example, styrene copolymers with acrylonitrile, butyl acrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid, acrylic acid, maleic anhydride, etc. Particularly preferred examples of the polymer include polystyrene, styrene-butyl acrylate copolymer, styrene-butyl methacrylate copolymer, and styrene-methyl methacrylate-butyl acrylate copolymer.

[0008] The molecular weight of the styrenic polymer is not particularly limited, but is 150,000 to 500,000, preferably 180,000 to 450,000, more preferably 250,000 to 450,000.
Styrene polymers in the range of 0000 to 400,000 are preferably used. If the molecular weight is smaller than this range, the effect of improving strength is small even if a resin in which terpene and vinyl aromatic hydrocarbon are copolymerized and the copolymer is hydrogenated is small, and a styrene-based polymer having a molecular weight higher than this range is used. The union is not preferable because the moldability deteriorates and the productivity of the styrene polymer itself decreases.

To produce the styrenic polymer (I) of the present invention, a known method for producing a styrenic resin, for example, a bulk polymerization method or a solution polymerization method is used. At this time, it is also possible to use a polymerization initiator commonly used in the production of styrene resins. In addition, a styrene-based polymer having a uniform composition using a complete mixing reactor frequently used in the production of copolymers, or a tubular reactor, or a combination polymerization of a complete mixing reactor and a tubular reactor is used. A styrene polymer having a non-uniform composition using an apparatus may be used. However, a styrene polymer having an opacity that greatly restricts the range of use, or a non-uniform composition that causes phase separation in extrusion, molding, or the like is not preferable. At this time, it is possible to maintain a usable transparency by using a method of additionally adding a raw material commonly used in the production of a styrene-based polymer and to control the composition to be non-uniform enough not to cause phase separation. is necessary.

The block copolymer (II) referred to in the present invention is a polymer block mainly composed of at least one vinyl aromatic hydrocarbon polymer block and at least one, preferably two or more conjugated dienes. And a block copolymer having: Here, the polymer block mainly composed of a conjugated diene is a polymer block having a conjugated diene content of 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more. Even if the vinyl aromatic hydrocarbon copolymerized in the conjugated diene-based polymer block is uniformly distributed in the polymer block,
Further, they may be distributed in a tapered shape. The weight ratio of vinyl aromatic hydrocarbon to conjugated diene in the block copolymer is 60:40 to 95: 5, preferably 60:40 to 9
If the vinyl aromatic hydrocarbon content of 0:10 is less than 60% by weight, the transparency of the styrene-based resin sheet is not practical. On the other hand, if it exceeds 95% by weight, the strength of the styrene-based resin sheet and the molded product obtained by molding the sheet will not be improved. It is also possible to use two or more block copolymers.

The weight of the vinyl aromatic hydrocarbon polymer block in the block copolymer is determined by a method of oxidizing the copolymer with di-t-butyl hydroperoxide using osmium tetroxide as a catalyst (for example, LM. KOLTHOF
F, et al. , J. et al. Polym. Sci. , 142
9 (1946)) and the like.

As the block copolymer used in the present invention, any of a linear block copolymer and a radial block copolymer can be used. The block copolymer can be basically produced by a conventionally known method. For example, JP-B-36-19386, JP-B-43-14779, and JP-B-48-2
No. 423, JP-B-48-4106, JP-B-4
9-36957 and the like.

In the present invention, styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, pt-butylstyrene and the like can be used as the vinyl aromatic hydrocarbon. These monomers may be used alone or in combination of two or more. In particular, a common one is styrene. The conjugated diene is a diolefin having a pair of conjugated double bonds. For example, 1,3-butadiene: 2-methyl-1,3-butadiene (isoprene); 2,3-dimethyl-1, 3-butadiene; 1,3
-Pentadiene; 1,3-hexadiene and the like can be used. You may use these individually or in mixture of 2 or more types. Particularly common are 1,3-butadiene,
Isoprene.

The styrene resin as the base material of the present invention can be obtained by blending the styrene polymer (I) and the block copolymer (II). The weight ratio of the styrene polymer to the block copolymer is 99.5: 0.5 to 50: 5.
It is in the range of 0. The weight ratio of the styrene polymer is 99.5.
When the amount exceeds 10% by weight, the effect of reinforcing the strength by the block copolymer is small, and the effect of improving the strength is not exhibited even when a terpene-based hydrogenated resin is added. On the other hand, if it is less than 50% by weight, it is not preferable in view of strength and cost of the styrene resin sheet.

When used as a uniaxially or biaxially stretched styrene resin sheet, the weight ratio of the styrene polymer to the block copolymer is 99.5: 0.5 to 70:
A range of 30 and more preferably a range of 99: 1 to 75:25 are suitably used. When used as a non-stretched styrene resin sheet, the weight ratio of the styrene polymer to the block copolymer is in the range of 90:10 to 20:80, and more preferably in the range of 80:20 to 30:70. It is preferably used.

The method of mixing the styrene polymer and the block copolymer is a known method, for example, mixing using an extruder, a Banbury mixer, or the like, or supplying two polymers to an extruder to form a styrene resin sheet. A method such as melt kneading at the stage of obtaining is used. A resin obtained by copolymerizing a terpene and a vinyl aromatic hydrocarbon and hydrogenating the copolymer (hereinafter, simply referred to as “terpene-based hydrogenated resin”. Table 2)
The same applies to In), styrene, α-methylstyrene and vinyltoluene are preferably used as vinyl aromatic hydrocarbons, and α-pinene, β-pinene and limonene alone or as a mixture can be suitably used as terpenes. The hydrogenation rate is not particularly limited, but is preferably 10% or more, preferably 20% or more. 10%
If it is less than 1, the color tone of the styrenic resin becomes unfavorable when exposed to high temperatures.

Although the degree of polymerization of the copolymer is not particularly limited, the degree of polymerization is 1,000 or less, preferably 500 or less, more preferably 200 or less. If the degree of polymerization exceeds 1,000, the compatibility with the styrene-based resin decreases, and the transparency decreases, which is not preferable. As the terpene-based hydrogenated resin, for example, Clearon M of Yashara Chemical Co., Ltd. can be used.

The terpene-based hydrogenated resin may be added by dissolving and polymerizing in a styrene-based monomer or a monomer mixture copolymerizable with the styrene-based monomer, a styrene-based polymer, or a styrene-based polymer. Melt the terpene-based hydrogenated resin during the polymerization of the terpene-based copolymer, or add the terpene-based hydrogenated resin by dissolving in a solvent, or before or after the polymerization is completed and unreacted styrene-based monomers are removed A method such as adding a hydrogenated resin can be used. It is also possible to mix a styrene resin and a terpene hydrogenated resin and knead them with an extruder or a molding machine.

The mixing ratio of the styrene resin and the terpene hydrogenated resin is 0.5 to 20 parts by weight, more preferably 0.5 to 15 parts by weight, per 100 parts by weight of the styrene resin. When the amount is less than 0.5 part by weight, no improvement in strength and secondary moldability is recognized, and when the amount exceeds 20 parts by weight, the cost of the resin increases, which is not preferable.

In order to produce the styrene resin sheet according to the present invention, a general method which has been frequently used, for example, a method of melting with an extruder and extruding from a T-die is used. The thickness of the sheet is not particularly limited, but is preferably in the range of 0.05 to 20 mm. Further, the sheet molded by the above method can be suitably used as a biaxially stretched styrene-based resin sheet having a draw ratio of 2 to 5 times by employing a generally known tenter method, inflation method or the like. .

The styrenic resin sheet according to the present invention has good moldability, and is made of a lightweight container by a conventional molding method such as vacuum forming, hot plate press forming (contact heating press forming) or indirect heating press forming. When molding a lid or the like, the molding cycle can be shortened. The styrenic resin sheet of the present invention has high sheet strength and does not cause cracking of the molded product during trimming. Further, since the strength of the molded product is improved, it is possible to make the thickness smaller than that of the conventional molded product.

Further, since the styrene resin of the present invention has good elongation during molding, it can be molded at a lower temperature than the conventional styrene resin. The heating time of the sheet is reduced, and consequently the molding cycle can be shortened. In obtaining the styrene resin sheet, a plasticizer, a lubricant, a pigment, an antistatic agent, a flame retardant, and the like may be mixed and used. Further, an antistatic agent, silicone, an antibacterial agent or the like may be applied to the surface of the obtained styrene resin sheet or the surface of the sheet molded product.

As long as the function of the styrene resin sheet intended in the present invention is not impaired, the specific styrene resin used in the present invention can be mixed with another styrene resin. Hereinafter, an example will be described in more detail.
However, the present invention is not limited by these examples.

[0024]

【Example】

(Styrene polymer-1) In a 10 L autoclave equipped with a stirrer, 5 kg of styrene, 0.2 kg of ethylbenzene,
After charging 1.2 g of 1,1 bis (t-butylperoxy) cyclohexane and polymerizing at 110 ° C. for 3 hours, 130 ° C. for 3 hours, and 150 ° C. for 2 hours, an unreacted styrene and ethylbenzene were recovered by an extruder, A styrenic polymer-1 is obtained.

The weight average molecular weight measured by GPC is 34.
6,000. (Styrene-based polymer-2) In a 10 L autoclave equipped with a stirrer, 4 kg of styrene, 1 kg of butyl acrylate,
Charge 0.3 kg of ethylbenzene and 1 g of 1,1 bis (t-butylperoxy) cyclohexane,
After polymerization at 130 ° C. for 3 hours and at 150 ° C. for 2 hours, unreacted styrene, butyl acrylate, and ethylbenzene are recovered by an extruder to obtain a styrene polymer-2.

The weight average molecular weight measured by GPC is 33
7,000. (Block copolymer-1 and -2) A styrene-butadiene block copolymer having a polymer structure and styrene content as shown in Table 1 is polymerized in n-hexane using n-butyllithium as an initiator. .

[0027]

Example-1 to Example-6, Comparative Example-1 to Comparative Example-5
The styrene resin was obtained by mixing at the ratio shown in Table 2 and granulating with a 20 mm twin screw extruder. Using this styrene resin, extrude with a 50 mmφ sheet extruder, 0.3 m thick
Create a sheet of m, 1.2 mm.

A 1.2 mm sheet is thermoformed using a hot plate pressure forming machine. Heating pressure 1.0 Kg / cm ^2, in heating the sheet, hinge 3R of molding pressure 2.5 Kg / cm ^2, molding time 2 seconds, and molded under the conditions of mold temperature 60 ° C., the mold (Food Pack) Hot plate temperature 1 that can be reproduced as mold
The heating time at 20 ° C. was determined, and the results are shown in Table 3. or,
Using a 0.3mm sheet, transparency, impact strength,
The bending strength was determined, and the results are shown in Table 3.

When the resin of Comparative Example-5 is formed into a sheet, the mineral oil bleeds out on the sheet surface, and the sheet surface is contaminated with oil droplets. In other cases, a sheet having a good appearance is obtained.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

The strength of the styrene resin sheet of the present invention, particularly in the direction perpendicular to the sheet extrusion direction, is remarkably improved while maintaining transparency. The styrene resin sheet of the present invention can be molded in a shorter time than a sheet using a conventional plasticizer. As a result, the molding cycle can be shortened. Further, at the time of sheet molding, the plasticizer and the like do not bleed out on the sheet surface, and the appearance is good.

Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display (C08L 25/04 93:00 53:02) 25:00

Claims (1)

(57) [Claims] 1. A styrene-based polymer (I), wherein the at least 1
Having at least one vinyl aromatic hydrocarbon polymer block and at least one conjugated diene-based polymer block, wherein the weight ratio of vinyl aromatic hydrocarbon to conjugated diene is 60: 4.
A resin composition comprising a block copolymer (II) having a ratio of 0 to 95: 5, wherein the weight ratio of the styrene-based polymer (I) to the block copolymer (II) is 99.5: 0.5 to 5
Molded with a styrene-based resin composition containing 0.5 to 20 parts by weight of a resin obtained by copolymerizing a terpene and a vinyl aromatic hydrocarbon and hydrogenating the copolymer per 100 parts by weight of a styrene-based resin having a ratio of 0:50. A styrene-based resin composition sheet having excellent strength and transparency.