JP4458879B2 - Styrenic heat-resistant resin foam sheet and method for producing the same - Google Patents

Description

  The present invention relates to an extruded foam sheet of a resin composition containing a styrene-methacrylic acid copolymer as a main component and a method for producing the same.

  A sheet obtained by extruding and foaming a resin composition containing a styrene-methacrylic acid copolymer as a main component is molded and used in a food container mainly used for microwave heating because it is excellent in heat resistance and heat insulation.

  When forming an extruded foam sheet of a resin composition containing a styrene-methacrylic acid copolymer as a main component into a container, the elongation at the time of heating is insufficient. When trying to shorten the heating time, the container may crack.

As an improvement measure, a method of adding a resin mainly composed of methyl methacrylate having a specific weight average molecular weight or more to a styrene-methacrylic acid copolymer having a specific composition has been proposed. Not enough.
JP-A-10-87929

  The problem to be solved is to improve the deep drawability of an extruded foam sheet of a resin composition containing a styrene-methacrylic acid copolymer as a main component.

  The present invention provides an epoxidized soybean oil and / or epoxidized linseed oil and, if necessary, a higher grade, in order to improve the deep drawability of an extruded foam sheet of a resin composition mainly composed of a styrene-methacrylic acid copolymer. The main feature is the addition of a fatty acid metal salt and extrusion.

  Since the foamed sheet of the resin composition mainly composed of the styrene-methacrylic acid copolymer produced by the production method of the present invention has improved deep drawability, the occurrence of cracks during container molding can be prevented. Also, the heating time can be shortened to improve the molding productivity.

  The styrene-methacrylic acid copolymer targeted by the present invention has a methacrylic acid unit content of 4 to 11% by mass. If it is less than 4% by mass, the heat resistance is poor, and the characteristic that it can be used for microwave heating is lost. Moreover, when it exceeds 11 mass%, brittleness will become strong and it will become difficult to prevent the crack generation at the time of container shaping | molding even if the manufacturing method of this invention is applied. The methacrylic acid unit content is measured by the method described in JP-A-8-28332.

  Although there is no restriction | limiting in particular in the weight average molecular weight of polystyrene conversion of this copolymer, 150,000-400,000 are preferable. If it is less than 150,000, the brittleness becomes strong, and even if the production method of the present invention is applied, it is difficult to prevent the occurrence of cracks during container molding. If it exceeds 400,000, the amount of extrusion per unit time is extremely reduced. The weight average molecular weight in terms of polystyrene is measured by gel permeation chromatography according to a conventional method.

  The copolymer may contain a small amount of a copolymerizable monomer as long as the properties of the copolymer are not impaired.

  The resin composition mainly composed of a styrene-methacrylic acid copolymer targeted by the present invention includes rubber-reinforced components such as HI-PS resin and MBS resin, and styrene such as SBS. About several percent of the thermoplastic elastomer may be contained.

In the present invention, the epoxidized soybean oil and the epoxidized linseed oil are added singly or in combination, and the addition amount is 0.005 to 0.005 based on the resin composition containing a styrene-methacrylic acid copolymer as a main component. 0.5 parts by mass. More preferably, it is 0.01-0.3 mass part.
When the amount is less than 0.005 parts by mass, the deep drawability of the finished foam sheet becomes insufficient. On the other hand, when the amount is more than 0.5 parts by mass, the increase in viscosity in the extruder becomes remarkable, and extrusion may be difficult.

  There is no particular limitation on the method of adding epoxidized soybean oil or epoxidized linseed oil to the extruder, and it may be added directly to the feed hole of the extruder, or it is mainly composed of a styrene-methacrylic acid copolymer. It can also be added together with the resin composition. Moreover, the masterbatch which used MS resin (styrene-methyl methacrylate copolymer) etc. whose styrene content is about 25-90 mass% etc. as a base material can be created, and it can also supply using the masterbatch. Moreover, it can also supply using the rubber | gum reinforcement | strengthening styrene resin and styrene thermoplastic elastomer which were previously mix | blended with epoxidized soybean oil and epoxidized linseed oil.

  In the present invention, a higher fatty acid metal salt can be used in combination in order to promote the reaction between the epoxidized soybean oil or epoxidized linseed oil and the styrene-methacrylic acid copolymer. The amount used in combination is preferably about the same as that of epoxidized soybean oil or epoxidized linseed oil, and even if added more, the accelerating effect is saturated. That is, the addition amount in this invention is 0-0.5 mass part with respect to the resin composition which has a styrene-methacrylic acid copolymer as a main component. More preferably, it is 0.01-0.3 mass part.

  Examples of the higher fatty acid metal salt used in the present invention include higher fatty acid zinc having 8 to 22 carbon atoms, magnesium, calcium, lithium, and aluminum. Higher fatty acid zinc and higher fatty acid magnesium, which are highly effective in promoting the reaction of epoxidized soybean oil or epoxidized linseed oil with styrene-methacrylic acid copolymer, are particularly preferred.

  There is no particular restriction on the method of adding the higher fatty acid metal salt to the extruder, and it may be added directly to the feed hole of the extruder alone or together with the resin composition mainly composed of a styrene-methacrylic acid copolymer. You can also Moreover, the masterbatch which uses MS resin (styrene-methyl methacrylate copolymer) etc. whose styrene content is about 25-90 mass% etc. as a base material can be created, and it can supply using the masterbatch. Moreover, it can also supply using the rubber | gum reinforcement | strengthening styrene-type resin and styrene-type thermoplastic elastomer which were previously mix | blended with the higher fatty acid metal salt.

  Reactions of higher fatty acid metal salts when fed to an extruder using a masterbatch premixed with epoxidized soybean oil or epoxidized linseed oil and higher fatty acid metal salts, or a rubber-reinforced styrene resin or styrene thermoplastic elastomer Since the accelerating effect may be poor, it is preferable that the epoxidized soybean oil or epoxidized linseed oil and the higher fatty acid metal salt are not subjected to a heat history in advance.

  As the nucleating agent for foaming, talc, calcium carbonate, sodium hydrogen carbonate, clay, citric acid or the like can be used alone or as a mixture, and talc is most preferable. There is no particular limitation on the method of adding the nucleating agent to the extruder, and it may be added directly to the feed hole of the extruder, or it may be added together with the resin composition containing a styrene-methacrylic acid copolymer as a main component. . Moreover, the masterbatch which used MS resin (styrene-methyl methacrylate copolymer) etc. whose styrene content is about 25-90 mass% etc. as a base material can be created, and it can also supply using the masterbatch. Moreover, you may mix | blend a higher fatty acid metal salt beforehand in this masterbatch. Lubricants such as ethylene bisstearylamide, spreading agents such as liquid paraffin and silicone oil, other surfactants, antistatic agents, antioxidants, plasticizers, light fasteners, pigments and the like may be included.

  As the production apparatus used in the production method of the present invention, a known extruded foam sheet production apparatus is suitable. That is, a known melt-kneading apparatus such as a single screw extruder or a twin screw extruder can be used alone or in combination of two or more.

  When implementing this invention, the preset temperature of the extruder cylinder until it press-fits a foaming agent is especially important, and it is preferable to set to 200 to 270 degreeC. More preferably, it is 220-250 degreeC. If the temperature is lower than 200 ° C., the reaction does not proceed sufficiently, and the resulting foam sheet may not have sufficient deep drawability. On the other hand, when the temperature is higher than 270 ° C., the reaction proceeds so much that extrusion may be difficult.

Example 1
Styrene unit content 92% by mass, methacrylic acid unit content 8% by mass, weight average molecular weight 230,000, melt mass flow rate (MFR) 1.6 g / 10 min styrene-methacrylic acid copolymer (T080 manufactured by Toyo Styrene Co., Ltd.) ) Talc (SP-manufactured by Kihara Kasei Co., Ltd. having a volume-based median diameter of 7 μm) with respect to a resin composition comprising 97% by mass and 3% by mass of SBS resin (TAFPRENE 125 manufactured by Asahi Kasei Chemicals Corporation). GB _SS ) 1 part by mass and epoxidized soybean oil (VIKOFLEX 7170 sold by Akishima Chemical Co., Ltd.) 0.1 part by mass and magnesium stearate (magnesium stearate GR: Mg-st manufactured by Nippon Oil & Fats Co., Ltd.) 0.1 part by mass Is fed into a 40 mm diameter single screw extruder (cylinder temperature 230 ° C.), melted and mixed, and then 3 parts by weight of butane gas as a blowing agent It was injected. Thereafter, it was transferred to a 65 mm diameter single screw extruder (cylinder temperature 120 ° C.), cooled, and then extruded from a circular die and foamed to obtain a foamed sheet having a thickness of 2 mm and a density of 0.1 g / cm 3. The melt mass flow rate (MFR) of the styrene-methacrylic acid copolymer (T080 manufactured by Toyo Styrene Co., Ltd.) was measured under the conditions of 200 ° C. and 49 N load according to JIS K 7210.

  The obtained foamed sheet is heated at a heater temperature of 260 ° C. for a predetermined time using a vacuum molding machine, softened and secondarily foamed, and then immediately vacuum-formed to form a circular bowl-shaped container having an inner diameter of 100 mm and a depth of 50 mm. Obtained. Observe the occurrence of cracks on the inner surface of the container, out of 100 molded containers, the number of cracks observed is 0, ◎ less than 5, ≧ 5 and less than 10 Table 1 shows the results of evaluating deep drawability with Δ being Δ and 10 or more.

Example 2
The same procedure as in Example 1 was performed except that the amount of epoxidized soybean oil was 0.2 parts by mass, magnesium stearate was not added, and the cylinder temperature was 240 ° C.

Example 3
Example 1 was the same as Example 1 except that the amount of epoxidized soybean oil was 0.01 parts by mass and the amount of magnesium stearate was 0.01 parts by mass.

Example 4
Example 1 was repeated except that the epoxidized soybean oil was changed to epoxidized linseed oil (Newsizer 512 manufactured by Nippon Oil & Fats Co., Ltd.).

Example 5
MBS resin (KCA603 manufactured by Rohm and Haas) was used instead of SBS resin, and the same procedure as in Example 1 was performed except that epoxidized soybean oil and magnesium stearate were not added. In addition, 1% of epoxidized soybean oil is added to the MBS resin in advance in the production process.

Example 6
Styrene-methyl methacrylate copolymer with a styrene unit content of 42% by mass, a methyl methacrylate unit content of 58% by mass, a weight average molecular weight of 170,000, and a melt mass flow rate (MFR) of 2.0 g / 10 min. company Ltd. TX-100) 50 wt%, volume-based median diameter (dv50) is 7μm talc (Kihara Kasei Co., Ltd. _SP-GB SS) 45 wt%, magnesium stearate 3% by weight, 2% by weight of liquid paraffin Mix for 5 minutes in a tumbler. The mixed composition was subjected to a kneader rotation speed of 250 rpm, a kneader cylinder temperature of 150 to 180 ° C., a ruder rotation speed of 60 rpm, a ruder cylinder temperature of 180 ° C., and a discharge rate of about 400 kg / hr using an extruder OCM100 manufactured by Nagata Seisakusho. , Melt-kneaded and pelletized. The obtained foam nucleating agent-containing thermoplastic resin composition is referred to as talc MB. In addition, the melt mass flow rate (MFR) of the styrene-methyl methacrylate copolymer (TX-100 manufactured by Denki Kagaku Kogyo Co., Ltd.) was measured in accordance with JIS K 7210 under the conditions of 200 ° C. and 49 N load.

  A styrene-methacrylic acid copolymer (Toyo Styrene Co., Ltd., T080) 97% by mass and an SBS resin (Asahi Kasei Chemicals Co., Ltd., Toughprene 125) 3% by mass were replaced with a styrene-methacrylic acid copolymer (Toyo S080) manufactured by Styrene Co., Ltd. 100% by mass, except that 1 part by mass of talc was replaced by 3 parts by mass of talc MB, and magnesium stearate was not added.

Example 7
Styrene unit content 42 mass%, methyl methacrylate unit content 58 mass%, weight average molecular weight 170,000 styrene-methyl methacrylate copolymer (Denki Chemical Co., Ltd. TX-100) 60 mass% and MBS resin ( 40% by mass of KCA603 manufactured by Rohm and Haas Co., Ltd. was mixed with a tumbler for 5 minutes. The mixed composition was melt-kneaded and pelletized using a 40 mm single screw extruder under the conditions of a screw speed of 100 rpm, a cylinder temperature of 230 ° C., and a discharge rate of about 20 kg / hr. The obtained thermoplastic resin composition is referred to as MBS-MB.

  A styrene-methacrylic acid copolymer (Toyo Styrene Co., Ltd., T080) 97% by mass and an SBS resin (Asahi Kasei Chemicals Co., Ltd., Toughprene 125) 3% by mass were replaced with a styrene-methacrylic acid copolymer (Toyo Styrene Co., Ltd. T080) 92% by mass, MBS-MB 8% by mass, except that 1 part by mass of talc was replaced by 3 parts by mass of talc MB, and epoxidized soybean oil and magnesium stearate were not added. Same as above.

Example 8
Example 1 was repeated except that the cylinder temperature was 210 ° C.

Example 9
Instead of the styrene-methacrylic acid copolymer (T080 manufactured by Toyo Styrene Co., Ltd.), the styrene unit content is 90% by mass, the methacrylic acid unit content is 10% by mass, the weight average molecular weight is 280,000, and the melt mass flow rate (MFR) is 0. The same procedure as in Example 6 was conducted except that a styrene-methacrylic acid copolymer (T100 manufactured by Toyo Styrene Co., Ltd.) was used at 4 g / 10 min. The melt mass flow rate (MFR) of the styrene-methacrylic acid copolymer (T100 manufactured by Toyo Styrene Co., Ltd.) was measured under the conditions of 200 ° C. and 49 N load according to JIS K 7210.

Example 10
Epoxidized soybean oil (Nippon Yushi) was replaced with 0.1 parts by mass of epoxidized soybean oil (VIKOFLEX 7170 sold by Akishima Chemical Co., Ltd.) and 0.1 parts by mass of magnesium stearate (magnesium stearate GR manufactured by Nippon Oil & Fat Co., Ltd.). Example 1 was the same as Example 1 except that 0.1 part by mass of New Sizer 510R) and 0.1 part by mass of zinc stearate (Zinc stearate G: Zn-st manufactured by Nippon Oil & Fats Co., Ltd.) were used.

Example 11
Instead of a resin composition consisting of 97% by mass of a styrene-methacrylic acid copolymer (T080 manufactured by Toyo Styrene Co., Ltd.) and 3% by mass of SBS resin (Tough Plain 125 manufactured by Asahi Kasei Chemicals Co., Ltd.), a styrene-methacrylic acid copolymer ( Toyostyrene Co., Ltd. T080) 100% by mass and the same as Example 1 except that magnesium stearate was not added.

Comparative Example 1
Example 1 was repeated except that epoxidized soybean oil and magnesium stearate were not added.

Comparative Example 2
The procedure was the same as Example 1 except that epoxidized soybean oil and magnesium stearate were not added and the cylinder temperature was 260 ° C.

Comparative Example 3
Example 1 was repeated except that epoxidized soybean oil was not added.

Comparative Example 4
Example 2 was the same as Example 2 except that the amount of epoxidized soybean oil was 0.7 parts by mass.

Comparative Example 5
Instead of the styrene-methacrylic acid copolymer (T080 manufactured by Toyo Styrene Co., Ltd.), the styrene unit content 96.5% by mass, the methacrylic acid unit content 3.5% by mass, the weight average molecular weight 260,000, the melt mass flow rate ( MFR) Same as Example 1 except that 1.6 g / 10 min styrene-methacrylic acid copolymer (T035 manufactured by Toyo Styrene Co., Ltd.) was used. The melt mass flow rate (MFR) of the styrene-methacrylic acid copolymer (T035 manufactured by Toyo Styrene Co., Ltd.) was measured under the conditions of 200 ° C. and 49 N load in accordance with JIS K 7210.

  The extruded foam sheet of the resin composition mainly comprising a styrene-methacrylic acid copolymer obtained by the production method of the present invention is less prone to cracking in the container even if the sheet heating time during container molding is short. Excellent squeezability. The results of Examples 2 to 11 and Comparative Examples 1 to 4 are also shown in Table 1.

  The heat resistance was compared using the containers having a heating time of 7 seconds obtained in Example 1 and Comparative Example 5. Salad oil heated to a predetermined temperature in increments of 5 ° C. was poured to about 80% of the container, and the temperature at the limit at which the salad oil was discarded after 1 minute was measured. The container of Example 1 was 130 ° C., whereas the container of Comparative Example 5 was as low as 120 ° C.

Claims (2)

0.005 to 0.5 parts by mass of epoxidized soybean oil and / or epoxidized linseed oil and 0 with respect to a resin composition having a methacrylic acid unit of 4 to 11% by mass of a styrene-methacrylic acid copolymer as a main component A method for producing a styrene-based heat-resistant resin foamed sheet, comprising adding ~ 0.5 part by mass of a higher fatty acid metal salt having 8 to 22 carbon atoms , heating, melting and extruding. A styrene heat-resistant resin foam sheet obtained by the production method according to claim 1.