JPS5898223A - Biaxially stretched styrene resin sheet - Google Patents

Abstract

PURPOSE:To obtain the sheet excellent in transparency, printability, releasability by stretching biaxially styrene resin composition with 0.2-0.5wt% rubber concentration obtained by adding 0.1-0.5wt% methyl phenyl polysiloxane to a mixture of rubber modified polystyrene and styrene copolymer. CONSTITUTION:Styrene resin composition with 0.2-0.5wt% rubber concentration obtained by adding 0.1-0.5wt% methyl phenyl polysiloxane to a mixture of graft copolymer with 5-9wt% rubber concentration having styrene grafted to the styrene bitadiene rubber containing 20-40wt% styrene and styrene copolymer is stretched biaxially. Thus, it is possible to obtain biaxially-stretched styrene resin sheet excellent in transparency, printability and releasability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a biaxially oriented styrenic resin sheet, particularly a copolymer obtained by grafting styrene onto styrene-butadiene rubber,
111 sl for a biaxially stretched styrenic resin sheet with excellent transparency, printability, and mold releasability, which is obtained by biaxially stretching a styrenic resin composition containing a styrene polymer and methylphenylpolysiloxane.

Conventionally, biaxially oriented polystyrene sheets have been widely used for food packaging because they have excellent transparency and stiffness, and do not contain harmful substances. However, when forming a large number of containers from these sheets, then stacking a large number of sheets, punching them, and then filling them with articles, the molded products have poor abrasiveness, work efficiency is low, and it is difficult to use force. There were gaps that could cause tearing of the molded product if peeled off. During this period, attempts were made to improve this by adding various additives, such as wax, oil, and plasticizers, but none of the equipment was satisfactory, and if they were used in large quantities, There was a problem that cloudy air occurred. When using a commercially available biaxially oriented polystyrene sheet y, a silicone emulsion is applied to the sheet for the purpose of imparting a release effect. However, according to this method, countless adhesion spots of silicone oil emulsion occur on the sheet surface, which reduces the commercial value of the sheet and molded product. In addition to this, there were problems in subsequent processing, such as printing and heat sealing.

The present invention solves these drawbacks, and
A graft copolymer (hereinafter referred to as rubber-modified polystyrene) with a rubber concentration of 5 to 9 weight %, which is obtained by grafting styrene onto styrene-butadiene rubber containing 40 weight % styrene;
A styrenic resin composition uniformly mixed with a transparent styrene polymer and methylphenylpolysiloxane is biaxially stretched, resulting in excellent transparency and sheet release properties, as well as suitability for stamping and heat sealing, which were previously difficult to achieve. It is an object of the present invention to provide a biaxially oriented styrenic resin sheet having excellent effects.

That is, in the present invention, 0.1 to 0.5% by weight of methylphenylpolysiloxane is added to a mixture of immodified listyrene and a styrene polymer at a rubber concentration of 0.2 to 0.5% by weight.
It is characterized by biaxial stretching of a 0.5 weight ratio styrene resin composition.

The styrenic resin composition according to the present invention, which will be described in further detail below, is a mixture of rubber-modified polystyrene, a styrene polymer, and methylphenyl polysiloxane (hereinafter abbreviated as MFPS), and the rubber-modified polystyrene is a mixture of styrene Content rate is 20-40 weight l1
It is a graft copolymer in which styrene is grafted onto tqb's styrene butadiene rubber and has a PIA degree of 5 to 9 times, and MFP8 Y O, 1 to 0 based on the total amount of this and a general type styrene polymer. .5 parts by weight are mixed to give an im concentration of 0.2 to 0.5 i1 parts.

The styrene-butadiene rubber used in the present invention needs to have a weight ratio of styrene to butadiene in the range of 40/60 to 20/80. When the proportion of styrene exceeds 40%, the effect of roughening the surface becomes weaker.
The ratio of styrene is 20 parts! If it is less than t%, it is difficult to maintain transparency.

The im average particle size is preferably 2 to 6 microns; if it is less than 2 microns, it will have transparency but its physical properties will deteriorate, and if it exceeds 6 microns, the transparency will decrease.

In general, styrenic polymers mixed with a small amount of synthetic rubber are extruded from a die into a sheet shape, forming fine irregularities on the surface. Are the particles stretched flat and transparent like synthetic rubber? There is almost no difference from the polystyrene biaxially stretched sheet that does not contain the polystyrene, and unevenness occurs on the surface of the sheet to the extent that it does not impair gloss. It is known that the unevenness of this surface improves the sheet's shapeability.
It also varies depending on the concentration and particle size of the synthetic rubber, and it is thought that the higher the trueness of the rubber, the more effective it is. However, as the imme concentration increases, the transparency of the stretched sheet decreases. Imke of normal particle size is added more than before,
In order to maintain transparency without causing unevenness on the surface, which is expected to be effective, it is essential to use a synthetic rubber material whose oil wetting rate is as close as possible to that of the base polystyrene.

The rubber concentration of the styrene thread used in the present invention is Y0.
The reason for specifying 2% to 0.5% overlap is that it is a sheet with a degree of stiffness that does not impair the transparency of conventional biaxially oriented polystyrene sheets, more specifically, a sheet with a thickness of 0.02 cIn. , ASTM D-1005 method 4
In order to obtain a biaxially stretched gelatin with a degree of haze of 1% or less, the rubber concentration of the styrene resin must be 0.5% or less.

In addition, in order to enhance the mold release effect, it is necessary to have a certain level of unevenness on the surface of the sheet, as in the case of abrasion, and it is necessary to add a graft copolymer of styrene and styrene-butadiene rubber of TS or higher. It is.

As an additive that improves the mold release effect, MFP8
Use Y. This is because the oil wetting rate is close to that of styrene polymer, and as the amount added increases, stuttering and clouding phenomena hardly occur. In order to achieve the same mold release effect, a weight i of 0.1"iL'Mk% or more is required, and 0.1"iL'Mk% or more is required.
．． If the amount is less than 1 volt, the effect will not be improved. Although there is no upper limit to the amount added, if it exceeds 0.5 weight factor, no increase in effect can be expected even if the amount added is increased.

Biaxial stretching as used in the present invention refers to the generally known tenter-type biaxial stretching method and the inflation method.
Refers to biaxial stretching performed by an axial stretching method or the like. The normal stretching method is 2.5 to 5 in both the vertical and horizontal directions using a tenter.
In the culture and inflation method, both vertically and horizontally 2 to 30
They are often obtained in a wide range and are appropriately selected depending on the purpose. The principle of the present invention is effective regardless of the stretching method.

Using the 2IIIl stretched sheet obtained by the method described above, a large number of containers are formed using a hot plate forming machine, stacked, and punched using a die press. [I found that in terms of releasability, there was no difference at all in terms of releasability from that of a sheet with a silicone oil emulsion for can shapes dropped on the surface.Furthermore, when this sheet was applied to Y printing, the printability was A'+7) Dense layer The quality was excellent, and no uneven printing occurred at all. In this way, completely contradictory effects of mold releasability and printability were produced.

The present invention will be further explained below with reference to Examples.

Examples 1 to 16 Immodified polystyrene consisting of a graft copolymer in which styrene is grafted to a polybutadiene rubber containing 6141% polybutadiene rubber with an average rubber particle size of 2μ or 6μ Denki Kagaku Kogyo Co., Ltd. product name [Dencastyrol HRM-6J and
In the mixing bowl, methylphenylpolysiloxane=kO,
By adding 1,0,3 t% of rubber, the rubber concentration was made to be 0.2 to 0.5 weight.

This resin was manufactured by V*Shiba Machine Co., Ltd. under the trade name of SN Knee 65J. The transparency of the sheet is MU STM-
As a result of measurement according to the D-1003 method, the cloudiness was 1 or less, which was good.

In addition, the sheet was formed using a hot plate pressure air forming machine (manufactured by Kansai Jidoki Co., Ltd., part name [px-400J), and then 20 sheets each were stacked and punched using a die press, using an automatic packaging machine Fuji Pack System Co., Ltd. A packaging test was carried out using RA-22J, a product manufactured by Co., Ltd., under the trade name, and the results showed that the packaging was perfectly smooth and there was no problem with the peelability between the molded products.

Further, the sheet was printed using a gravure printing machine manufactured by Higashiya Tekko Co., Ltd. and immersed in the Toyo Ink Co., Ltd. brand name [Styrene BJ11']. As a result, there was no peeling of the plate, and the print finish was good. In addition, the ink layer density Y [solid results were good] using commercially available Tedeke.

The results are shown in Table 1.

Table 1 Comparative Examples 1 to 10 The type of rubber in the graft copolymer of the example was changed to polybutadiene, and the resin was mixed with 0.1 to 0.6 weights so that the average rubber particle diameter was 2μ and 6μ. Then, a stretched sheet was prepared, and then a silicone oil emulsion (manufactured by Shin-Etsu Silicone Co., Ltd., trade name rKM-787Jv) was applied to this.
The coating was carried out under the same conditions as in the example.

Although the results are shown in Comparative Example Experiment' in Table 2, no product satisfying transparency, patternability, and printability was obtained.

Table 2 The physical properties shown in Tables 1 and 2 of Examples and Comparative Examples were obtained by the following method.

(1) Transparency Compliant with A8TM v-1005 law! 6 (4t)I
? (*) Indicated.

(2) Mold releasability The evaluation was based on the number of troubles the automatic packaging machine had.

◎　0 times for 200 trays 0 1 to 6 times Δ 6-10 (b) × 10 or more times There isn't.

2...... Approximately % peels off 1...
...Applicant for patent that almost completely peels off Denki Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] Styrene-t-grafted styrene-butadiene rubber containing 20-40% by weight of styrene was added to a mixture of a graft copolymer and a styrene electropolymer with a haze level of 5-9% by weight, and 0.1% of methylphenylpolysiloxane was added. 1. A biaxially stretched styrenic resin sheet characterized by biaxially stretching a styrenic resin composition containing 0.5 to 0.5 times more of rubber and having a rubber concentration of 0.2 to 0.5M.