JP7474036B2 - Styrene-unsaturated carboxylic acid resin, resin composition thereof, extruded sheet and molded product - Google Patents

Description

The present invention relates to a styrene-unsaturated carboxylic acid resin, a resin composition thereof, and non-foamed and foamed extruded sheets and molded articles formed using the styrene-unsaturated carboxylic acid resin.

Styrene-unsaturated carboxylic acid resins, such as styrene-acrylic acid, have excellent heat resistance and are inexpensive, so they are widely used in food packaging materials for boxed lunches and prepared foods, foam boards for residential insulation, and diffusion panels for LCD televisions that contain diffusion agents. In recent years, with the spread of commercial microwave ovens in convenience stores and other places, and due to the shortening of microwave oven operating times, higher output devices (easier to reach higher temperatures in a shorter time) are being used. For this reason, there is a demand for resins that are more heat resistant and have excellent moldability.

However, in styrene-unsaturated carboxylic acid resins, it is necessary to increase the unsaturated carboxylic acid content to improve heat resistance. However, in exchange for imparting heat resistance by increasing the unsaturated carboxylic acid content, there is a trade-off in that moldability deteriorates due to an increase in the melt viscosity of the resin, and the increase in gelled matter due to dehydration condensation between unsaturated carboxylic acid side chains leads to poor sheet appearance and reduced mechanical strength. For example, Patent Document 1 discloses a method of copolymerizing methyl methacrylate, and Patent Document 2 discloses a method of adding a branched aliphatic primary alcohol with 14 to 20 carbon atoms and a freezing point of -10°C or lower.

Patent Publication 2011-126996 Patent Publication 2010-270179

The methods described in Patent Documents 1 and 2 reduce the appearance defects of the molded sheet to some extent. However, they are insufficient in terms of preventing deterioration of moldability and mechanical strength.

Therefore, the problem to be solved by the present invention is to provide a styrene-unsaturated carboxylic acid resin and resin composition having excellent heat resistance, mechanical strength and moldability, and an extruded sheet and molded product using the same.

As a result of intensive research conducted by the inventors in consideration of the above problems, they discovered a method for obtaining a styrene-unsaturated carboxylic acid-based resin with excellent moldability and mechanical strength, and an extruded sheet and molded product using the same, which is excellent in heat resistance while maintaining the improvement achieved by introducing an unsaturated carboxylic acid, by copolymerizing a small amount of an unsaturated carboxylic acid ester monomer having an ester substituent with 5 or more carbon atoms with a styrene-based monomer and an unsaturated carboxylic acid monomer, thereby completing the present invention.

That is, the present invention is as follows.
[1] In the present invention, there is provided a styrene-unsaturated carboxylic acid-based resin comprising a styrene-based monomer unit, an unsaturated carboxylic acid monomer unit, and an unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms,
A styrene-unsaturated carboxylic acid resin, in which the content of the styrene-based monomer unit is 74 to 97.99% by mass, the content of the unsaturated carboxylic acid monomer unit is 2 to 18% by mass, and the content of the unsaturated carboxylic acid ester monomer unit is 0.01 to 8.0% by mass, when the total content of the styrene-based monomer unit, the unsaturated carboxylic acid monomer unit, and the unsaturated carboxylic acid ester monomer unit is 100% by mass.
[2] In the present invention, the styrene-unsaturated carboxylic acid resin according to the above [1], wherein the content of the unsaturated carboxylic acid ester monomer unit is 0.05% to 5.0%.
[3] In the present invention, the styrene-unsaturated carboxylic acid resin according to the above [1] or [2], wherein the content of the unsaturated carboxylic acid monomer unit is 4 to 16 mass %.
[4] In the present invention, the styrene-unsaturated carboxylic acid resin according to any one of the above [1] to [3] has a melt mass flow rate of 0.5 to 4.5 g/10 min.
[5] In the present invention, the styrene-unsaturated carboxylic acid resin according to any one of the above [1] to [4] has a Vicat softening temperature of 105° C. or higher.
[6] In the present invention, the styrene-unsaturated carboxylic acid resin according to any one of [1] to [5] above, having a weight average molecular weight (Mw) of 100,000 to 350,000.
[7] In the present invention, there is provided a styrene-unsaturated carboxylic acid resin composition comprising the styrene-unsaturated carboxylic acid resin according to any one of [1] to [6] above and a monohydric alcohol having 5 to 13 carbon atoms,
The styrene-unsaturated carboxylic acid resin composition according to any one of the above [1] to [6], wherein the content of the styrene-unsaturated carboxylic acid resin is 100 parts by mass, and the monohydric alcohol having 5 to 13 carbon atoms is 0.001 to 0.06 parts by mass.
[8] In the present invention, there is provided a composition comprising the styrene-unsaturated carboxylic acid resin according to any one of [1] to [6] above and a monohydric alcohol having 16 or more carbon atoms,
The styrene-unsaturated carboxylic acid resin composition according to any one of the above [1] to [6], containing 0.1 to 1.0 parts by mass of the monohydric alcohol having 16 or more carbon atoms when the content of the styrene-unsaturated carboxylic acid resin is 100 parts by mass.
[9] In the present invention, a non-foamed extruded sheet having the styrene-unsaturated carboxylic acid resin according to any one of [1] to [6] above or the styrene-unsaturated carboxylic acid resin composition according to [7] or [8] above.
[10] In the present invention, a foamed extruded sheet having the styrene-unsaturated carboxylic acid resin according to any one of [1] to [6] above or the styrene-unsaturated carboxylic acid resin composition according to [7] or [8] above.
[11] In the present invention, a molded product formed using the non-foamed extruded sheet according to the above [9] or the foamed extruded sheet according to the above [10].

According to the present invention, it is possible to provide a styrene-unsaturated carboxylic acid resin having excellent heat resistance, mechanical strength and moldability.
According to the present invention, it is possible to provide a styrene-unsaturated carboxylic acid based resin composition, a foamed extruded sheet, a non-foamed extruded sheet and a molded article, which are excellent in appearance, mechanical strength and moldability.

FIG. 1 is a diagram showing a method for measuring stiffness of a tray container in this embodiment.

The following describes in detail the form for carrying out the present invention (hereinafter, referred to as the "present embodiment"). Note that the present invention is not limited to the following embodiment, and can be carried out in various modifications within the scope of the gist of the invention.

[Styrene-unsaturated carboxylic acid resin]
One aspect of the present invention provides a styrene-unsaturated carboxylic acid resin containing a styrene-based monomer unit, an unsaturated carboxylic acid monomer unit, and an unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms, the content of the styrene-based monomer unit being 74 to 97.99% by mass, the content of the unsaturated carboxylic acid monomer unit being 2 to 18% by mass, and the content of the unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms being 0.01 to 8.0% by mass, when the total content of the styrene-based monomer unit, the unsaturated carboxylic acid monomer unit, and the unsaturated carboxylic acid ester monomer unit is taken as 100% by mass. That is, the styrene-unsaturated carboxylic acid resin according to the present invention is a copolymer having three repeating units, a styrene-based monomer unit, an unsaturated carboxylic acid monomer unit, and an unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms.

<<Unsaturated Carboxylic Acid Ester Monomer Unit>>
In this embodiment, the unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms plays a role in improving moldability by reducing the melt viscosity of the resin and improving mechanical strength. When the total content of the styrene monomer unit, the unsaturated carboxylic acid monomer unit, and the unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms is taken as 100% by mass, the content of the unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms is 0.01 to 8.0% by mass, preferably 0.05 to 5.0% by mass, more preferably 0.08 to 2.0% by mass, and even more preferably 0.10 to 0.5% by mass. If this content is less than 0.01% by mass, the effect of reducing the viscosity of the resin and improving the mechanical strength cannot be obtained, and if it exceeds 8.0% by mass, the water absorption becomes high, causing bubbles in the molded product, and further the decrease in heat resistance also increases. In addition, when the decrease in heat resistance is suppressed and the effect of improving mechanical strength and fluidity is emphasized, it is preferable to suppress it to less than 0.5% by mass. When emphasis is placed on mechanical strength, the unsaturated carboxylic acid ester monomer is preferably a methacrylic acid ester monomer. In the present invention, moldability refers to fluidity.

The number of carbon atoms in the ester substituent is 5 or more, preferably 6 or more, more preferably 7 or more, and even more preferably 8 or more. If the number is less than 5, it is not possible to obtain a good balance between the mechanical strength and the effect of improving fluidity.

In this specification, "an unsaturated carboxylate monomer unit having an ester substituent having 5 or more carbon atoms" means a repeating unit derived from an unsaturated carboxylate monomer having an ester substituent having 5 or more carbon atoms. And, "an unsaturated carboxylate monomer having an ester substituent having 5 or more carbon atoms" means a carboxylate ester (R ¹ -C(═O)-O-R ² ) in which R ¹ has an unsaturated double bond and R ² is an ester substituent having 5 or more carbon atoms.

In this embodiment, the unsaturated carboxylate monomer unit having an ester substituent having 5 or more carbon atoms may contain a hetero bond such as carbon-oxygen, carbon-nitrogen, or carbon-sulfur, or an unsaturated bond, as the chemical structure of the functional group other than the polymerizable group (R ¹ -C(═O)-O-). The unsaturated carboxylate monomer having an ester substituent having 5 or more carbon atoms in the present invention is preferably a compound represented by the following general formula (1).

（上記一般式（１）中、Ｒ^aは、水素原子又は炭素原子数１～３のアルキル基を表わし、Ｒ²は、炭素原子数５以上のエステル置換基を表わし、当該炭素原子数５以上のエステル置換基としては、炭素原子数５～５０の直鎖状又は分岐状アルキル基を表わすことが好ましい。上記エステル置換基の炭素原子数としては、好ましくは６～４０、より好ましくは７～３０、より更に好ましくは８～２０である。炭素原子数を５以上にすることで成形性（流動性）の向上効果が得られ、５０以下にすることによって耐熱性の低下を抑えることができる。炭素原子数を８～２０の範囲にすることで、流動性と機械強度の向上効果をバランスよく得ることができる。なお、炭素原子数５～５０の直鎖状又は分岐状アルキル基中の各－ＣＨ₂－は独立して酸素原子が２以上連続して結合されないよう－Ｏ－に置換されてもよい。）
本実施形態において、上記一般式（１）中、Ｒ^aとしては、水素原子、メチル基、エチル基、プロピル基が挙げられるが、重合性の観点から水素原子又はメチル基が好ましく、より好ましくは耐熱性向上の観点からメチル基である。

(In the above general formula (1), R ^a represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ² represents an ester substituent having 5 or more carbon atoms, and the ester substituent having 5 or more carbon atoms is preferably a linear or branched alkyl group having 5 to 50 carbon atoms. The number of carbon atoms of the ester substituent is preferably 6 to 40, more preferably 7 to 30, and even more preferably 8 to 20. By making the number of carbon atoms 5 or more, an effect of improving moldability (fluidity) can be obtained, and by making the number of carbon atoms 50 or less, a decrease in heat resistance can be suppressed. By making the number of carbon atoms within the range of 8 to 20, an effect of improving fluidity and mechanical strength can be obtained in a well-balanced manner. Note that each -CH ₂ - in the linear or branched alkyl group having 5 to 50 carbon atoms may be independently replaced with -O- so that two or more oxygen atoms are not consecutively bonded.)
In this embodiment, in the above general formula (1), R ^a may be a hydrogen atom, a methyl group, an ethyl group, or a propyl group. From the viewpoint of polymerizability, a hydrogen atom or a methyl group is preferable, and from the viewpoint of improving heat resistance, a methyl group is more preferable.

In this embodiment, in the above general formula (1), R ² may be an n-pentyl group, an isopentyl group, a 2-methylbutyl group, an n-hexyl group, a 2-methylpentyl group, an n-heptyl group, a 2,2-dimethylbutyl group, an n-heptyl group, a 2-methylhexyl group, a 2-ethylheptyl group, an n-octyl group, a 2-ethylhexyl group, a 1-ethylhexyl group, an n-nonyl group, a 2-ethylheptyl group, an n-dodecyl group, a stearyl group, a cyclohexyl group, a polyethylene glycol monoether group, a cyclohexene group, etc. Among these, the structure of the ester substituent R ² is preferably a branched alkyl group having 5 or more carbon atoms, including a branched structure having a large free volume, or a polyethylene glycol, from the viewpoint of improving flowability, and is preferably a linear alkyl group from the viewpoint of suppressing a decrease in heat resistance.

For example, examples of unsaturated carboxylic acid ester monomers having an ester substituent having 5 or more carbon atoms include n-pentyl (meth)acrylate, isopentyl (meth)acrylate, 2-methylbutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-methylpentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, 1,2,2,6,6-pentamethyl-4-piperidyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, 3-sulfopropyl potassium (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, polyethylene glycol (meth)acrylate, and cyclohexene (meth)acrylate.

In this embodiment, the polyethylene glycol (meth)acrylates preferably have a structure represented by the following general formula (2):

(In the above general formula (2), R represents a linear or branched alkyl group having 12 to 20 carbon atoms, and X represents the average number of ethylene oxides added and is an integer of 4 to 12.)
<<Styrene-based monomer unit>>
In this embodiment, when the total content of the styrene-based monomer units, the unsaturated carboxylic acid monomer units, and the unsaturated carboxylic acid ester monomer units having an ester substituent having 5 or more carbon atoms is taken as 100 mass%, the content of the styrene-based monomer units is 74 to 97.99 mass%, preferably 77 to 97 mass%, and more preferably 80 to 96 mass%. If this content is less than 74 mass%, the fluidity of the resin decreases, and if it exceeds 97.99 mass%, the unsaturated carboxylic acid monomer units described below cannot be present in a desired amount.

The styrene monomer is not particularly limited, but examples thereof include styrene, α-methylstyrene, β-methylstyrene, paramethylstyrene, orthomethylstyrene, metamethylstyrene, chlorostyrene, bromostyrene, etc. From an industrial viewpoint, styrene and α-methylstyrene are particularly preferred, and styrene is more preferred. As the styrene monomer, these can be used alone or in a mixture of two or more kinds.

<<Unsaturated Carboxylic Acid Monomer Unit>>
In this embodiment, the unsaturated carboxylic acid monomer unit plays a role in improving heat resistance. When the total content of the styrene monomer unit, the unsaturated carboxylic acid monomer unit, and the unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms is taken as 100% by mass, the content of the unsaturated carboxylic acid monomer unit is 2 to 18% by mass, preferably 3 to 17% by mass, and more preferably 4 to 16% by mass. If this content is less than 2% by mass, the effect of improving heat resistance is insufficient. In addition, if the content of the unsaturated carboxylic acid monomer unit exceeds 18% by mass, it is not preferable because it increases gelled matter in the resin or increases water absorption, which leads to the generation of bubbles during molding.

Examples of unsaturated carboxylic acid monomers include acrylic acid and methacrylic acid. From an industrial point of view, these may be used alone or in combination as the unsaturated carboxylic acid monomer. Methacrylic acid is particularly preferred as the unsaturated carboxylic acid monomer, as it has a large effect of improving heat resistance.

The styrene-unsaturated carboxylic acid resin according to the present invention may have monomer units other than the three repeating units of the styrene monomer unit, the unsaturated carboxylic acid monomer unit, and the unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms described above. That is, in this embodiment, as long as it is copolymerizable with a styrene monomer, an unsaturated carboxylic acid monomer, an ester substituent having 5 or more carbon atoms, or an unsaturated carboxylic acid ester monomer unit, even if the ester substituent has 4 or less carbon atoms, it may be copolymerized with a monomer other than the three monomers shown above, without any particular limitation, as long as the effect of the invention is not impaired. For example, examples of monomers other than the three monomers listed above include vinyl compounds such as maleic anhydride, maleic acid, fumaric acid, itaconic acid, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and (meth)acrylonitrile, as well as dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleic anhydride, maleimide, and nucleus-substituted maleimide. Among these, (meth)acrylic acid ester compounds are preferred.

The content of styrene-based monomer units, unsaturated carboxylic acid monomer units, unsaturated carboxylic acid ester monomer units having an ester substituent with 5 or more carbon atoms, and other monomer units in a styrene-unsaturated carboxylic acid resin can be determined from the integral value of the spectrum when the resin is measured by pyrolysis GC-MS.

In this embodiment, the weight average molecular weight (Mw) of the styrene-unsaturated carboxylic acid resin is preferably 100,000 to 400,000, and more preferably 120,000 to 320,000. When the weight average molecular weight is 100,000 to 350,000, a resin with excellent practical balance between impact strength and fluidity is obtained. The weight average molecular weight can be measured by gel permeation chromatography in terms of standard polystyrene.

[Styrene-unsaturated carboxylic acid resin composition]
One aspect of the present invention is a styrene-unsaturated carboxylic acid resin composition (hereinafter, sometimes simply referred to as a resin composition). More specifically, the resin composition preferably contains a styrene-unsaturated carboxylic acid resin containing a styrene monomer unit, an unsaturated carboxylic acid monomer unit, and an unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms, and a predetermined monohydric alcohol. By allowing the styrene-unsaturated carboxylic acid resin according to the present invention to coexist with the monohydric alcohol, the generation of a gelled product during molding is suppressed.

<<Alcohols having 5 to 13 carbon atoms>>
In a preferred aspect of this embodiment, the resin composition contains the styrene-unsaturated carboxylic acid resin according to the present invention and a monohydric alcohol having 5 to 13 carbon atoms.

In this embodiment, monohydric alcohols having 5 to 13 carbon atoms suppress the formation of gelled matter during molding at around 200°C, resulting in molded products with better appearance. As the monohydric alcohol, monohydric alcohols having 5 to 13 carbon atoms are preferred. Alcohols having 4 or fewer carbon atoms have a higher polarity than styrene-based resins and can cause turbidity. On the other hand, alcohols having 14 or more carbon atoms produce an odor during molding, etc., which reduces workability.

The carbon chain constituting the alcohol may contain heteroatoms such as oxygen or nitrogen, and may contain bonds other than single bonds, such as double bonds, triple bonds, ester bonds, and amide bonds. The number of carbon atoms in the carbon chain is more preferably 6 to 12, and particularly preferably 8 to 11. The monohydric alcohol may be contained in the styrene-unsaturated carboxylic acid resin composition. Therefore, the monohydric alcohol may be present (or added) in the polymerization solution used in polymerizing the styrene-unsaturated carboxylic acid resin, so that the monohydric alcohol remains in the resin composition, which is the final product, or may be contained by mixing in an extruder or solvent after polymerization of the styrene-unsaturated carboxylic acid resin.

Examples of monohydric alcohols having 5 to 13 carbon atoms include, but are not limited to, n-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-pentanol, 2-methyl-2-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 3-methyl-3-pentanol, 2,2-dimethyl-1-butanol, 2,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, 1-octanol, 2-ethyl-1-hexanol, 6-methyl-1-heptanol, 2-methylheptan-2-ol, 1-nonanol, 3-methyloctan-3-ol, 1-decanol, 1-undecanol, 1-dodecanol, 1-tridecanol, 1-methoxy-2-propanol, 2-aminoethanol, 6-amino-hexanol, 2-(methylamino)ethanol, diethanolamine, 1,3-diamino-2-propanol, 2-(ethylthio)ethanol, 2-(propylthio)ethanol, cyclohexanol, benzyl alcohol, 3-methyl-3-buten-1-ol, 3-hydroxy-3-methyl-1-butene, allyl alcohols, etc.

The boiling point of the monohydric alcohol having 5 to 13 carbon atoms is preferably 130°C to 240°C, more preferably 140°C to 240°C, and even more preferably 150°C to 230°C. If the boiling point is less than 130°C, it tends to cause resin clouding, and if it is more than 290°C, it may cause odors during molding.

The content of the monohydric alcohol having 5 to 13 carbon atoms in the styrene-unsaturated carboxylic acid resin composition according to the present invention is preferably 0.001 to 0.06 parts by mass, more preferably 0.005 to 0.05 parts by mass, and even more preferably 0.01 to 0.04 parts by mass, when the content of the styrene-unsaturated carboxylic acid resin is 100 parts by mass. If the content of the monohydric alcohol is less than 0.001 parts by mass, the gel suppression effect decreases, and the high volatility of more than 0.06% by mass may cause odors during molding.

<<Monohydric alcohols having 16 or more carbon atoms>>
In a preferred aspect of this embodiment, the styrene-unsaturated carboxylic acid resin composition preferably contains the styrene-unsaturated carboxylic acid resin according to the present invention and a monohydric alcohol having 16 or more carbon atoms. Alcohols having 15 or less carbon atoms are highly volatile, and the alcohol generates an odor during molding or the like, reducing workability. However, it has been confirmed that by increasing the number of carbon atoms to 16 or more, the volatility is reduced and the unpleasant odor during molding or the like is suppressed.

In this embodiment, the inclusion of a monohydric alcohol having 16 or more carbon atoms suppresses the formation of gelled matter during molding at around 250°C, and a molded product with excellent appearance can be obtained. The monohydric alcohol is an alcohol having 16 or more carbon atoms and containing one hydroxyl group, and may contain heteroatoms such as oxygen or nitrogen in the carbon chain, and may contain bonds other than single bonds, such as double bonds, triple bonds, ester bonds, and amide bonds in the carbon chain. The number of carbon atoms is preferably 16 or more, more preferably 17 or more. Even more preferably, it is 18 to 50. The monohydric alcohol may be contained in the styrene-unsaturated carboxylic acid resin composition. Therefore, the monohydric alcohol may be present (or added) in the polymerization solution used for polymerizing the styrene-unsaturated carboxylic acid resin, so that the monohydric alcohol remains in the resin composition, which is the final product, or may be contained by mixing in an extruder or solvent after polymerization of the styrene-unsaturated carboxylic acid resin.

In this embodiment, if molding at around 200°C or if emphasis is placed on suppressing turbidity, it is preferable to select an alcohol with 5 to 13 carbon atoms, and if molding at around 250°C or if emphasis is placed on suppressing odor, it is preferable to select an alcohol with 16 or more carbon atoms.

The boiling point of monohydric alcohols having 16 or more carbon atoms is preferably 260°C or higher, more preferably 270°C or higher, and even more preferably 290°C or higher. If the boiling point of alcohols is less than 260°C, they tend to be highly volatile and produce unpleasant odors during molding, etc.

The content of the monohydric alcohol having 16 or more carbon atoms in the styrene-unsaturated carboxylic acid resin composition according to the present invention is preferably 0.1 to 1.0 part by mass, more preferably 0.1 to 0.7 parts by mass, and even more preferably 0.1 to 0.4 parts by mass, when the content of the styrene-unsaturated carboxylic acid resin is 100 parts by mass. If the content is less than 0.1 part by mass, the gel suppression effect during molding at around 250°C decreases, and if it exceeds 1.0 part by mass, the amount remaining in the resin increases, causing an unpleasant odor or a significant decrease in heat resistance, and the effect of increasing heat resistance due to methacrylic acid modification becomes poor.

Examples of monohydric alcohols having 16 or more carbon atoms include, but are not limited to, 1-hexadecanol, isohexadecanol, 1-octadecanol, 5,7,7-trimethyl-2-(1,3,3-trimethylbutyl)-1-octanol, isooctadecanol, 1-isoisoeicosanol, 8-methyl-2-(4-methylhexyl)-1-decanol, 2-heptyl-1-undecanol, 2-heptyl-4-methyl-1-decanol, 2-(1,5-dimethylhexyl)-(5,9-dimethyl)-1-decanol, and polyethylene glycol monoethers.

The styrene-unsaturated carboxylic acid resin composition according to the present invention contains a styrene-unsaturated carboxylic acid resin, an alcohol having 5 to 13 carbon atoms, and a monohydric alcohol having 16 or more carbon atoms, and preferably contains 0.001 to 0.06 parts by mass of the alcohol having 5 to 13 carbon atoms and 0.1 to 1.0 parts by mass of the monohydric alcohol having 16 or more carbon atoms, when the content of the styrene-unsaturated carboxylic acid resin is taken as 100 parts by mass.

<Other ingredients>
In addition to the monohydric alcohol, the styrene-unsaturated carboxylic acid resin composition of the present embodiment may be made into a styrene-unsaturated carboxylic acid resin composition by adding various additives generally used in styrene-based resins to achieve known effects. Examples of such additives include stabilizers, antioxidants, ultraviolet absorbers, lubricants, release agents, plasticizers, antiblocking agents, antistatic agents, antifogging agents, and mineral oils. Reinforcing materials such as styrene-butadiene block copolymers or MBS resins may also be added to the extent that the physical properties are not impaired. There are no particular restrictions on the method of blending, but examples include a method in which the additives are added during polymerization and polymerized, or a method in which the additives are mixed in advance in a blender before melt-kneading after polymerization, and then melt-kneaded in an extruder or Banbury mixer.

In this embodiment, various additives can be added to the styrene-unsaturated carboxylic acid resin composition as described above, but the content of the styrene-unsaturated carboxylic acid resin in the styrene-unsaturated carboxylic acid resin composition is not particularly limited, but is preferably 95% by mass or more, more preferably 97% by mass, and even more preferably 99% by mass or more.

<Physical Properties of Styrene-Unsaturated Carboxylic Acid Resin Composition>
In this embodiment, the Vicat softening temperature of the styrene-unsaturated carboxylic acid resin and the resin composition is preferably 105° C. or higher. By setting the temperature in this range, the composition can be suitably used as a food packaging material that comes into contact with hot water or hot oil. The Vicat softening temperature can be measured in accordance with ISO306 under conditions of a load of 50 N and a heating rate of 50° C./h.

In this embodiment, the melt flow rate of the styrene-unsaturated carboxylic acid resin and the resin composition at 200°C is preferably in the range of 0.5 to 4.5 g/10 min, more preferably 1.0 to 3.5 g/10 min, and even more preferably 1.5 to 2.5 g/10 min. By making the melt flow rate 0.5 g/10 min or more, good moldability can be obtained, and by making it 4.5 g/10 min or less, a resin with excellent strength can be obtained.

In this embodiment, the content of unreacted monomers generated and remaining during the production of the styrene-unsaturated carboxylic acid resin and the resin composition is preferably 0.1 parts by mass or less, more preferably 0.08 parts by mass or less, and even more preferably 0.06 parts by mass or less, when the total content of the styrene-based monomer unit, the unsaturated carboxylic acid monomer unit, and the unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms is taken as 100 parts by mass. By making the total amount of each unreacted monomer 0.1 parts by mass or less, the odor around the die outlet during sheet extrusion using the styrene-unsaturated carboxylic acid resin and the resin composition of this embodiment is improved. The color tone of the resin is also improved. The remaining amount of each monomer constituting the styrene-based resin can be measured by gas chromatography.

In the styrene-unsaturated carboxylic acid resin and resin composition according to the present invention, when the total content of the styrene monomer unit, the unsaturated carboxylic acid monomer unit, and the unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms is 100 parts by mass, the total amount of the remaining styrene dimer and trimer is 0.6 parts by mass or less, preferably 0.5 parts by mass or less, and more preferably 0.4 parts by mass or less. If the total amount of the remaining styrene dimer and trimer is 0.6 parts by mass or less, for example, in injection molding, the adhesion of styrene dimer and trimer to the mold is significantly reduced, the transfer of these dimers and trimers to the molded product is significantly reduced, and the appearance defect is significantly improved. In addition, in extrusion molding of sheets, etc., the amount of styrene dimer and trimer precipitated on the die is significantly reduced, the transfer to the sheet is significantly reduced, and the appearance defect is significantly improved. In addition, the need for cleaning the mold and die outlet can be reduced, so productivity is improved. Examples of styrene dimers and trimers include 1,3-diphenylpropane, 2,4-diphenyl-1-butene, 1,2-diphenylcyclobutane, 1-phenyltetralin, 2,4,6-triphenyl-1-hexene, and 1-phenyl-4-(1'-phenylethyl)tetralin. The remaining amount of styrene dimers and trimers can be measured by gas chromatography.

<Method of producing styrene-unsaturated carboxylic acid resin composition>
The method for producing the styrene-unsaturated carboxylic acid resin of this embodiment will be described below.
The method for producing a styrene-unsaturated carboxylic acid resin of the present invention preferably includes a step of preparing a mixed solution by mixing a styrene monomer, an unsaturated carboxylic acid monomer, an unsaturated carboxylic acid ester monomer having an ester substituent having 5 or more carbon atoms, a monohydric alcohol, and a first solvent, a polymerization step of polymerizing the mixed solution, and a step of recovering a reaction product.

There are no particular limitations on the polymerization method for styrene-unsaturated carboxylic acid resins, but for example, radical polymerization methods, particularly bulk polymerization and solution polymerization methods, can be preferably used.

Specifically, the polymerization method mainly comprises a polymerization process in which the polymerization raw materials (monomer components) are polymerized, and a devolatilization process in which volatile matters such as unreacted monomers and polymerization solvents are removed from the polymerization product.

The polymerization method according to this embodiment will be described below.
The raw materials for the styrene-based monomer unit, the unsaturated carboxylic acid monomer unit, and the unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms, which are the constituent units of the styrene-unsaturated carboxylic acid resin of this embodiment, are as described above, and will not be described here.

In this embodiment, when the polymerization raw materials are polymerized to obtain a styrene-unsaturated carboxylic acid resin, a polymerization initiator is typically contained in the polymerization raw material composition. Examples of the polymerization initiator include organic peroxides, for example, peroxyketals such as 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)cyclohexane, and n-butyl-4,4-bis(t-butylperoxy)valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide, diacyl peroxides such as acetyl peroxide and isobutyryl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyesters such as t-butylperoxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butyl hydroperoxide. From the viewpoint of decomposition rate and polymerization rate, 1,1-bis(t-butylperoxy)cyclohexane is particularly preferred.

When polymerizing styrene-unsaturated carboxylic acid resins, a chain transfer agent can be used as necessary. Examples of chain transfer agents include α-methylstyrene linear dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-octyl mercaptan.

As a polymerization method, solution polymerization using a polymerization solvent can be used. As the polymerization solvent, aromatic solvents such as toluene, ethylbenzene, propylbenzene, and butylbenzene are preferable, and if necessary, a solvent system in which the solubility of the styrene-unsaturated carboxylic acid resin is adjusted by combining polar solvents such as alcohols or ketones may be used.

As the above alcohols, monohydric alcohols are preferred. Examples of such alcohols include the above-mentioned monohydric alcohols having 5 to 13 carbon atoms and monohydric alcohols having 16 or more carbon atoms.

In this embodiment, the polymerization solvent is preferably used in the range of 3 to 35 parts by mass, more preferably 5 to 30 parts by mass, per 100 parts by mass of all monomers constituting the styrene-unsaturated carboxylic acid resin. If the polymerization solvent exceeds 35 parts by mass per 100 parts by mass of all monomers, the polymerization rate decreases and the molecular weight of the resulting resin also decreases, so the mechanical strength of the resin tends to decrease. In addition, if the polymerization solvent is less than 3 parts by mass, it may be difficult to control the heat removal during polymerization. Adding 3 to 35 parts by mass per 100 parts by mass of all monomers is preferable in terms of making the quality uniform and controlling the polymerization temperature.

When using a monohydric alcohol as a polymerization solvent, it is preferable to add it in a ratio of 1 to 10% by mass relative to 100% by mass of the total polymerization solvent.

In this embodiment, the amount of the styrene monomer charged is preferably 50 to 90 parts by mass relative to 100 parts by mass of the total monomers. The amount of the unsaturated carboxylic acid monomer charged is preferably 1 to 13 parts by mass relative to 100 parts by mass of the total monomers. The amount of the unsaturated carboxylic acid ester monomer having an ester substituent having 5 or more carbon atoms charged is preferably 0.1 to 5.0 parts by mass relative to 100 parts by mass of the total monomers. The amount of the other monomers charged is preferably 0 to 8 parts by mass relative to 100 parts by mass of the total monomers.

In this embodiment, the apparatus used in the polymerization step for obtaining the styrene-unsaturated carboxylic acid resin is not particularly limited, and may be appropriately selected in accordance with the polymerization method for the styrene-unsaturated carboxylic acid resin, taking into account the viscosity and heat removal. For example, in the case of bulk polymerization, one tower reactor or complete mixing reactor, or multiple reactors connected together, may be used.

In addition, in this embodiment, a devolatilization step may be performed after the polymerization step in which the styrene-unsaturated carboxylic acid resin is polymerized. There is no particular restriction on the devolatilization step. When the polymerization step is performed by bulk polymerization, the polymerization step is continued until the final amount of unreacted monomer is preferably 50 mass% or less, more preferably 40 mass% or less, and then, in the devolatilization step, devolatilization is performed by a known method to remove volatile matters such as unreacted monomer. For example, a normal devolatilization device such as a flash drum, a twin-screw devolatilizer, a thin film evaporator, or an extruder can be used, but a devolatilization device with a small retention portion is preferable. The temperature of the devolatilization treatment is usually about 150 to 280°C, preferably 160 to 260°C, and more preferably 160 to 240°C. By setting the devolatilization temperature to 150°C or higher, unreacted styrene monomer can be efficiently removed. In addition, by setting the devolatilization temperature to 280°C or lower, it is possible to suppress the low molecular weight caused by thermal decomposition of the styrene-unsaturated carboxylic acid resin.

The pressure in the devolatilization process is usually about 0.13 to 4.0 kPa, preferably 0.13 to 3.0 kPa, and more preferably 0.13 to 2.0 kPa. The residence time in the devolatilization process is usually less than 2.0 hours, preferably less than 1.5 hours, and more preferably less than 1.2 hours. By making the residence time in the devolatilization process less than 2.0 hours, it is possible to prevent the decomposition of the styrene-unsaturated carboxylic acid resin from progressing, resulting in a decrease in molecular weight or an increase in the monomer content of the composition. As a devolatilization method, for example, a method of removing volatiles by reducing pressure under heating, and a method of removing volatiles through an extruder or the like designed for the purpose of removing volatiles are desirable.

[Extruded sheet]
Another aspect of the present invention provides an extruded sheet formed using the above-mentioned styrene-unsaturated carboxylic acid resin and resin composition of the present invention. The extruded sheet may be either non-foamed or foamed. A commonly known method can be used as a method for producing an extruded sheet. A method using a single-screw or twin-screw extruder equipped with a T-die and a device for taking up a sheet with a uniaxial or biaxial stretching machine can be used as a method for producing a foamed extruded sheet, and a method using an extrusion foaming machine equipped with a T-die or circular die can be used as a method for producing a foamed extruded sheet.

When forming a foamed extrusion sheet, substances that are commonly used for foaming agents and foam nucleating agents during extrusion foaming can be used. Butane, pentane, freon, carbon dioxide, water, etc. can be used as the foaming agent, with butane being preferred. Talc, etc. can also be used as the foam nucleating agent.

The foamed extruded sheet preferably has a thickness of 0.5 mm to 5.0 mm, an apparent density of 50 g/L to 300 g/L, and a basis weight of 80 g/m ² to 300 g/m ^2. The foamed extruded sheet of the present invention may be multi-layered, for example, by further laminating a film. The type of film used may be any type commonly used for polystyrene.

On the other hand, for non-foamed extruded sheets, a thickness of, for example, about 0.1 to 1.0 mm is preferable from the viewpoint of rigidity and thermoforming cycle. The sheet may be formed only by ordinary low-magnification roll stretching, but in particular, a sheet that is stretched by about 1.3 to 7 times with a roll and then stretched by about 1.3 to 7 times with a tenter is preferable in terms of strength. It may also be used in a multilayer with a styrene-based resin such as polystyrene resin. It may also be used in a multilayer with a resin other than the styrene-based resin. Examples of resins other than the styrene-based resin include PET resin, nylon resin, and polyolefin resin.

Another aspect of the present invention provides a molded product formed using the non-foamed extruded sheet or foamed extruded sheet of the present invention described above. The foamed extruded sheet or a multi-layer body containing the same can be molded, for example, by vacuum forming to produce a container such as a tray. The non-foamed extruded sheet can also be molded, for example, by vacuum forming to produce a lid for a lunch box or a container for storing side dishes, etc.

The present invention will now be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The methods for analyzing and evaluating the resins and extruded sheets in the examples and comparative examples are as follows.

[Evaluation of properties of styrene-unsaturated carboxylic acid resin]
(1) Measurement of monomer units in copolymer which is a styrene-unsaturated carboxylic acid resin The content of each monomer unit in a copolymer containing a styrene monomer unit, an unsaturated carboxylic acid monomer unit, an unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms, and other monomer units which are optional components was measured under the following conditions.

Quantitative analysis was performed by a calibration curve method based on the integral value of the spectrum measured by pyrolysis GC-MS.
Measurement sample amount: 0.25 mg
Measurement equipment: Agilent CG-7890A, MSD-5975C, EGA/PA-3030D
Column: HP-5MS
Carrier: Helium Ionization method: EI
Oven temperature: 40°C, hold for 5 minutes → 20°C/min → 320°C, hold for 16 minutes Split ratio: 100/1
Thermal decomposition temperature: 600°C

(2) Measurement of Weight Average Molecular Weight of Styrene-Unsaturated Carboxylic Acid Resin The weight average molecular weight (Mw) of the styrene-unsaturated carboxylic acid resin was measured by gel permeation chromatography (GPC) under the following conditions.
Measuring equipment: Tosoh HLC-8220
Separation column: Two Tosoh TSK gel Super HZM-H (inner diameter 4.6 mm) connected in series Guard column: Tosoh TSK guard column Super HZ-H
Measurement solvent: tetrahydrofuran (THF)
Sample concentration: 5 mg of a measurement sample was dissolved in 10 mL of a solvent and filtered through a 0.45 μm filter.
Injection volume: 10 μL
Measurement temperature: 40°C
Flow rate: 0.35 mL/min Detector: Ultraviolet absorption detector (Tosoh UV-8020, wavelength 254 nm)
The calibration curve was created using 11 types of TSK standard polystyrene (F-850, F-450, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000) manufactured by Tosoh Corporation. The calibration curve was created using a linear approximation equation.

(3) Measurement of Melt Mass Flow Rate (MFR) The melt mass flow rates (g/10 min) of the styrene-unsaturated carboxylic acid resin and the resin composition were measured in accordance with ISO1133 at 200° C. and a load of 49 N.

(4) Measurement of Vicat Softening Temperature The Vicat softening temperature of the styrene-unsaturated carboxylic acid resin and the resin composition was measured in accordance with ISO 306. The load was 50 N, and the heating rate was 50° C./h.

(5) Measurement of the Content of Unreacted Monomer and Alcohols in Styrene-Unsaturated Carboxylic Acid Resin and/or Styrene-Unsaturated Carboxylic Acid Resin Composition The contents of the styrene monomer, the unsaturated carboxylic acid monomer, the unsaturated carboxylic acid ester monomer having an ester substituent having 5 or more carbon atoms excluding polymerizable groups, other monomers, and alcohols (monohydric alcohols) when the styrene-unsaturated carboxylic acid resin was taken as 100 mass % were measured using gas chromatography under the following conditions.
Sample preparation: 2.0 g of resin was dissolved in 20 mL of methyl ethyl ketone, and then 5 mL of methanol containing a standard substance (triphenylmethane) was added to reprecipitate the polymer component, and the supernatant was collected and used as the measurement solution.
Measurement equipment: Agilent 6850 series GC system Detector: FID
Column: HP-1 (100% dimethylpolysiloxane) 30 m,
Film thickness: 0.25 μm, 0.32 mm diameter
Injection volume: 1 μL (splitless)
Column temperature: 40°C for 2 minutes → heated to 320°C at 20°C/min →
Hold at 320°C for 15 minutes Injection port temperature: 250°C
Detector temperature: 280°C
Carrier gas: Helium

(6) Evaluation of odor at die outlet When a styrene-unsaturated carboxylic acid resin and a resin composition were used for sheet extrusion in a 30 mmφ short-axis sheet extruder, the odor at the die outlet was confirmed and evaluated according to the following evaluation criteria.

◯: Almost no odor detected ×: Odor detected

(7) Measurement of Water Absorption Rate The styrene-unsaturated carboxylic acid resin and the resin composition were injection molded into a plate of 5 cm × 12 cm × 0.2 cm, and the original mass was measured. After that, the plate was immersed in pure water for 7 days in a room kept at a room temperature of 23°C and a humidity of 50%, and the mass was measured and calculated according to the following formula (1).

[Non-foamed extrusion properties and non-foamed extrudate properties]
(8) Measurement of gel insoluble content in resin 2 g of styrene-unsaturated carboxylic acid resin and resin composition was dissolved in 20 ml of methyl ethyl ketone, centrifuged at 19,000 rpm for 60 minutes with a 43,000 G centrifuge, discarded the supernatant, added 20 ml of methyl ethyl ketone to the remaining liquid, and repeated the same operation (centrifuged at 19,000 rpm for 60 minutes). After discarding the supernatant, the remaining liquid was dried at 150° C. for 30 minutes, and then dried at 215° C. under reduced pressure of 3 kPa for 30 minutes. The gel insoluble content was measured by the following formula (2):

(9) Appearance Evaluation of Non-foamed Extruded Sheet Using a styrene-unsaturated carboxylic acid resin and a resin composition, a sheet was continuously extruded for 3 hours using a 30 mmφ short-axis sheet extruder, and then five sheets measuring 10 cm × 20 cm were cut out from the 0.3 mm thick sheet. The number of gels and air bubbles, which were foreign matter with an average diameter of (major axis + minor axis)/2 of 0.5 mm or more on the surfaces of the five sheets, was counted, and the appearance was evaluated by the following method.
○: Gel, number of bubbles 2 or less △: Gel, number of bubbles 3 to 9 ×: Gel, number of bubbles 10 or more

(10) Measurement of falling weight impact strength (kg cm) Using a styrene-unsaturated carboxylic acid-based resin and a resin composition, a sheet of 0.3±0.03 mm was prepared using a 25 mmφ single-screw sheet extruder (manufactured by Soken Co., Ltd.), and the falling weight impact strength was measured using a DuPont impact tester (No. 451) manufactured by Toyo Seiki Co., Ltd. The mass of the falling weight was 0.025 kg, the radius of the tip of the impact center was 6.3 mm, and the radius of the impact center receiving stand was 9.4 mm, and the falling weight impact strength was calculated as the 50% destruction value (mass of the falling weight 0.025 kg) x (height cm). For styrene-unsaturated carboxylic acid-based resins and resin compositions showing a falling weight impact strength of 0.6 kg cm or more, cracks were unlikely to occur during punching after forming into a container.

[Foam Extrudate Properties]
(11) Measurement of waist strength of tray container The waist strength of tray containers molded using styrene-unsaturated carboxylic acid resins and resin compositions was measured by the method shown in FIG. 1. More specifically, a tray container 1 formed by vacuum molding a foamed extrusion sheet expanded 7.3 times was compressed in the TD direction of the tray container 1 with a crosshead 2 at a compression speed of 5 mm/min, and the waist strength (N) of the tray container 1 was measured. The size of the tray container 1 was 10 cm long, 15 cm wide, and 2 cm deep. The tray container 1 was compressed from the lateral side, and the maximum load was taken as the waist strength. For styrene-unsaturated carboxylic acid resins and resin compositions showing a waist strength of 20 N or more, the containers tended to crack less during transportation.

(12) Appearance Evaluation of Foamed Extruded Sheet The surface roughness of the foamed extruded sheet was visually evaluated.
◯: roughness on the sheet surface is visible. ×: roughness on the sheet surface is not visible. Examples and comparative examples will now be described.

[Example 1]
A polymerization raw material composition liquid consisting of 76.9 parts by mass of styrene, 5.8 parts by mass of methacrylic acid, 14.2 parts by mass of 5,7,7-trimethyl-2-ethylbenzene, and 0.027 parts by mass of 1,1-di(t-butylperoxy)cyclohexane (PHC, NOF Corp., trade name: Perhexa (registered trademark) C) was continuously fed at a rate of 1.1 liters/hour to a polymerization apparatus consisting of a 4-liter complete mixing type reactor, and further to a devolatilizer connected to a single-screw extruder for removing volatile matters such as unreacted monomers and polymerization solvent, to synthesize a styrene-unsaturated carboxylic acid resin, which is a copolymer. The polymerization reaction conditions in the polymerization step were a polymerization temperature of 132°C for the complete mixing reactor. The polymer yield was 62.4% by mass, measured by (sample mass after drying/sample mass before drying×100%) after drying the final polymerization liquid at 230°C under reduced pressure of 3 kPa for 30 minutes. The final polymerization solution was extruded into pellets to obtain pellets 1 of a styrene-unsaturated carboxylic acid resin.

Using the obtained pellets 1, a non-foamed extrusion product (non-foamed extrusion sheet) and a foamed extrusion product (foamed extrusion sheet, and tray container as a molded product) were each produced, and their physical properties were evaluated. For the non-foamed extrusion sheet, a 30 mm short-screw extruder was used, and a sheet with a thickness of about 0.3 mm was produced while the temperature of the resin melting zone was set to 220 to 250°C and the pressure was reduced to 3 kPa from the vent using a vacuum pump. For the foamed extrusion sheet and tray container, an extrusion foaming machine equipped with a circular die with a diameter of 150 mm was used, and 0.12 parts by mass of talc (average particle size 1.3 μm) as a foaming nucleating agent and 3.5 parts by mass of liquefied butane as a foaming agent were added to 100 parts by mass of the obtained resin to produce a foamed extrusion sheet (foaming ratio: 7.5 times). The temperature of the resin melting zone was adjusted to 210 to 240°C, the rotary cooler temperature to 145 to 185°C, and the die temperature to 165°C. The resulting foamed extrusion sheet was used to vacuum mold a foamed tray container measuring 10 cm in length, 15 cm in width, and 2 cm in depth. The evaluation results of the properties of the non-foamed extrusion product and the foamed extrusion product are shown in Table 1-2.

[Example 2]
A polymerization raw material composition liquid consisting of 76.9 parts by mass of styrene, 5.8 parts by mass of methacrylic acid, 2-ethylhexyl methacrylate, 2.0 parts by mass of 2-ethylhexanol, 1.0 part by mass of 5,7,7-trimethyl-2-(1,3,3-trimethylbutyl)-1-octanol (Fine Oxocol 180 manufactured by Nissan Chemical Industries, Ltd.), 14.2 parts by mass of ethylbenzene, and 0.027 parts by mass of 1,1-di(t-butylperoxy)cyclohexane (PHC, manufactured by NOF Corporation, product name: Perhexa (registered trademark) C) was continuously supplied at a rate of 1.1 L/hour to a polymerization apparatus consisting of a complete mixing type reactor having a capacity of 4 L, and further to a devolatilizer connected to a single-screw extruder for removing volatile matters such as unreacted monomers and polymerization solvent, thereby synthesizing a styrene-unsaturated carboxylic acid resin composition containing a monohydric alcohol. The polymerization reaction conditions in the polymerization step were a polymerization temperature of 132° C. in the complete mixing reactor. The polymer yield was 62.1% by mass when measured by (sample mass after drying/sample mass before drying×100%) after drying the final polymerization liquid at 230° C. under reduced pressure of 3 kPa for 30 minutes. The final polymerization liquid was extruded into pellets to obtain pellets 2 of a styrene-unsaturated carboxylic acid-based resin composition.

Using the obtained pellets 2, a non-foamed extrusion product (non-foamed extrusion sheet) and a foamed extrusion product (foamed extrusion sheet, and tray container as a molded product) were each produced, and their physical properties were evaluated. For the non-foamed extrusion sheet, a 30 mm short-screw extruder was used, and a sheet with a thickness of about 0.3 mm was produced while the temperature of the resin melting zone was set to 220 to 250°C and the pressure was reduced to 3 kPa from the vent using a vacuum pump. For the foamed extrusion sheet and tray container, an extrusion foaming machine equipped with a circular die with a diameter of 150 mm was used, and 0.12 parts by mass of talc (average particle size 1.3 μm) as a foaming nucleating agent and 3.5 parts by mass of liquefied butane as a foaming agent were added to 100 parts by mass of the obtained resin to produce a foamed extrusion sheet (foaming ratio: 7.5 times). The temperature of the resin melting zone was adjusted to 210 to 240°C, the rotary cooler temperature to 145 to 185°C, and the die temperature to 165°C. The resulting foamed extrusion sheet was used to vacuum mold a foamed tray container measuring 10 cm in length, 15 cm in width, and 2 cm in depth. The evaluation results of the properties of the non-foamed extrusion product and the foamed extrusion product are shown in Table 1-2.

[Examples 3 to 24]
In Examples 3 to 24, pellets 3 to 24 of the styrene-unsaturated carboxylic acid resin composition were prepared in the same manner as in Example 2, except that the conditions were changed as shown in Table 1-1, and the properties and physical properties of the non-foamed extrudates and foamed extrudates were evaluated in the same manner as in Example 2. The evaluation results are shown in Table 1-2.

[Example 25]
In Example 25, a styrene-unsaturated carboxylic acid resin was obtained under the polymerization conditions shown in Table 1-1, and then 0.025 parts by mass of 2-ethyl-1-hexanol and 0.200 parts by mass of Fine Oxocol manufactured by Nissan Chemical Industries, Ltd. were extruded and kneaded in a twin-screw extruder per 100 parts by mass of the styrene-unsaturated carboxylic acid resin to prepare pellets 25 of a styrene-unsaturated carboxylic acid resin composition, and the properties and physical properties of the non-foamed extrudate and the foamed extrudate were evaluated in the same manner as in Example 2. The evaluation results are shown in Table 1-2.

[Comparative Examples 1 to 4]
Styrene-based resin compositions 1 to 4 were prepared in the same manner as in Example 2, except that the conditions were changed as shown in Table 2-1, and the properties and physical properties of the non-foamed extrudates and foamed extrudates were evaluated in the same manner as in Example 2. The evaluation results are shown in Table 2-2. In Comparative Examples 1 to 4, the monomer units constituting the resin did not contain a (meth)acrylic acid ester monomer unit having 5 or more carbon atoms excluding the polymerization group, so that the effects of improving the falling weight impact strength and reducing the viscosity were not obtained.

[Comparative Example 5]
A styrene-based resin composition was prepared under the same conditions as in Example 2, except that the conditions were changed as shown in Table 2-1, and the properties and physical properties of the non-foamed extrudates and foamed extrudates were evaluated in the same manner as in Example 2. The evaluation results are shown in Table 2-2. Compared with the styrene-unsaturated carboxylic acid-based resin compositions 2 to 24 obtained in Examples 2 to 24, the styrene-based resin composition 5 obtained in Comparative Example 5 did not achieve an improvement in the falling weight impact strength and a decrease in the viscosity when n-butyl acrylate (C4) was used as the (meth)acrylic acid ester monomer unit.

[Comparative Examples 6 and 7]
Styrenic resin compositions 6 and 7 were prepared under the same conditions as in Example 2, except that the conditions were changed as shown in Table 2-1, and the properties and physical properties of the non-foamed extrudates and foamed extrudates were evaluated in the same manner as in Example 2. The evaluation results are shown in Table 2-2. In a resin having an unsaturated carboxylic acid monomer unit content of 1% in the styrene resin, no improvement in the falling weight impact strength and no reduction in viscosity were obtained even when the resin contained 0.2% of a (meth)acrylic acid ester monomer unit having 5 or more carbon atoms excluding the polymerization group.

[Comparative Examples 8 and 9]
Styrene-based resin compositions 8 and 9 were prepared under the same conditions as in Example 2, except that the conditions were changed as shown in Table 2-1, and the properties and physical properties of the non-foamed extrudates and foamed extrudates were evaluated in the same manner as in Example 2. The evaluation results are shown in Table 2-2. In a resin having an unsaturated carboxylic acid monomer unit content of 20% in the styrene-based resin, the effect of improving the falling weight impact strength and reducing the viscosity was not obtained even when the resin contained 0.2% of a (meth)acrylic acid ester monomer unit having 5 or more carbon atoms excluding the polymerization group.

[Comparative Example 10]
A styrene-based resin composition 10 was prepared under the same conditions as in Example 2, except that the conditions were changed as shown in Table 2-1, and the properties and physical properties of the non-foamed extrudate and the foamed extrudate were evaluated in the same manner as in Example 2. The evaluation results are shown in Table 2-2. When the (meth)acrylic acid ester monomer unit having 5 or more carbon atoms was 10% by mass, the water absorption rate was high, and the appearance of the extruded sheet after molding was deteriorated.

[Comparative Examples 11 to 12]
The styrene-unsaturated carboxylic acid resin obtained in Example 1 was extruded and kneaded with 1-tetradecanol in Comparative Example 11 and 1-pentadecanol in Comparative Example 12 in the same manner as in Example 25 so that the alcohol content was 0.121 parts by mass and 0.134 parts by mass, respectively, to obtain styrene-based resin compositions 11 and 12. However, an odor was generated during extrusion molding, and the odor evaluation result at the die outlet was "x", so the evaluation was discontinued. Note that the odor evaluation results at the die outlet in all of Examples 1 to 25 and Comparative Examples 1 to 10 were "○".

The styrene-unsaturated carboxylic acid resin obtained by the present invention has excellent heat resistance, mechanical strength, and moldability (fluidity). The styrene-unsaturated carboxylic acid resin composition obtained by the present invention has excellent heat resistance, mechanical strength, fluidity, and appearance after molding. Therefore, the styrene-unsaturated carboxylic acid resin composition of the present invention can be widely used for non-foamed or foamed sheets even in extrusion molding, food packaging containers using them, or molded products by injection molding (electrical product parts, toys, daily necessities, various industrial parts), and plays a major role in the industrial world.

1 Tray container 2 Crosshead

Claims (11)

A styrene-unsaturated carboxylic acid resin comprising a styrene monomer unit, an unsaturated carboxylic acid monomer unit, and an unsaturated carboxylic acid ester monomer unit having an ester substituent having 5 or more carbon atoms,
the content of the styrene-based monomer unit is 80 to 97.99 mass%, the content of the unsaturated carboxylic acid monomer unit is 2 to 18 mass%, and the content of the unsaturated carboxylic acid ester monomer unit is 0.01 to 2.0 mass%, when the total content of the styrene-based monomer unit, the unsaturated carboxylic acid monomer unit, and the unsaturated carboxylic acid ester monomer unit is 100 mass%,
The styrene-based monomer unit is a monomer unit represented by styrene, β-methylstyrene, paramethylstyrene, orthomethylstyrene, metamethylstyrene, chlorostyrene, or bromostyrene. 2. The styrene-unsaturated carboxylic acid resin according to claim 1, wherein the content of the unsaturated carboxylic acid ester monomer unit is 0.05 to 2.0% by mass . The styrene-unsaturated carboxylic acid resin according to claim 1 or 2, wherein the content of the unsaturated carboxylic acid monomer unit is 4 to 16 mass %. The styrene-unsaturated carboxylic acid resin according to any one of claims 1 to 3, having a melt mass flow rate of 0.5 to 4.5 g/10 min. The styrene-unsaturated carboxylic acid resin according to any one of claims 1 to 4, having a Vicat softening temperature of 105°C or higher. The styrene-unsaturated carboxylic acid resin according to any one of claims 1 to 5, having a weight average molecular weight (Mw) of 100,000 to 350,000. A styrene-unsaturated carboxylic acid resin composition comprising the styrene-unsaturated carboxylic acid resin according to any one of claims 1 to 6 and a monohydric alcohol having 5 to 13 carbon atoms,
The styrene-unsaturated carboxylic acid resin composition according to any one of claims 1 to 6, wherein the styrene-unsaturated carboxylic acid resin contains 0.001 to 0.06 parts by mass of the monohydric alcohol having 5 to 13 carbon atoms when the content of the styrene-unsaturated carboxylic acid resin is 100 parts by mass. A composition comprising the styrene-unsaturated carboxylic acid resin according to any one of claims 1 to 6 and a monohydric alcohol having 16 or more carbon atoms,
The styrene-unsaturated carboxylic acid resin composition according to any one of claims 1 to 6, wherein the styrene-unsaturated carboxylic acid resin contains 0.1 to 1.0 parts by mass of the monohydric alcohol having 16 or more carbon atoms when the content of the styrene-unsaturated carboxylic acid resin is 100 parts by mass. A non-foamed extruded sheet having the styrene-unsaturated carboxylic acid resin according to any one of claims 1 to 6 or the styrene-unsaturated carboxylic acid resin composition according to claim 7 or 8. A foamed extruded sheet having the styrene-unsaturated carboxylic acid resin according to any one of claims 1 to 6 or the styrene-unsaturated carboxylic acid resin composition according to claim 7 or 8. A molded product formed using the non-foamed extruded sheet according to claim 9 or the foamed extruded sheet according to claim 10.