JP5860585B2 - Polystyrene resin sheet - Google Patents

Description

  The present invention relates to a polystyrene resin sheet having at least a surface formed of a polystyrene resin composition containing a base resin composed of at least one of polystyrene resins and a polymer type antistatic agent.

Conventionally, various polystyrene resin sheets such as a foam sheet and a non-foam film made of a polystyrene resin composition, and a laminate sheet in which the foam sheet and the film are laminated and integrated have been used in various applications. Yes.
Since such polystyrene resin sheets are excellent in heat resistance and mechanical strength, they have been widely used in curing sheets, assembly boxes, partition materials, electrical / electronic component containers, mechanical component containers, food containers, and the like. It is used.
However, polystyrene-based resin films and foamed sheets are easily charged by static electricity, and have a problem that dirt or the like easily adheres during storage, and improvement is required.

It is known that such problems due to the charging of the polystyrene resin sheet can be prevented by lowering the value of the surface resistivity of the sheet surface. Although the value is usually a level exceeding 10 ¹⁵ (Ω / □) order, it is reduced to about 10 ¹³ (Ω / □) order (less than 1 × 10 ¹⁴ Ω / □). It is known that such problems can be reduced.
In addition, the polystyrene-based resin sheet may require a surface resistivity of the order of 10 ¹¹ (Ω / □) depending on the application.

As a technique for reducing the surface resistivity, a method of incorporating a component called an antistatic agent in a resin composition used for forming a polystyrene-based resin sheet has been adopted. Conventionally, a component such as a surfactant is contained in a raw material. It is made to contain.
Those having a molecular weight of about 1000 or less, such as this surfactant, are also referred to as “low molecular antistatic agents”, and these low molecular antistatic agents are effective for antistatic. Since the diffusion rate in the polymer is high, there is a possibility that a problem of so-called “bleed out” occurs due to oozing on the surface of the polystyrene resin sheet with time.

In recent years, instead of a low molecular weight antistatic agent, the use of a so-called “polymeric antistatic agent” whose main component is a high molecular weight material having a molecular weight exceeding 1000 and reaching several tens of thousands. (See Patent Document 1 below).
As this polymer type antistatic agent, a copolymer having a polar block containing an ether bond or an ester bond and a nonpolar block made of alkyl or the like is known. Such a copolymer is a polymer. Since the transferability in the inside is low, the effect of suppressing the bleed-out problem can be expected by using this polymer type antistatic agent.
In addition to such copolymer resins, it is known that, for example, ionomer resins can be used as polymer antistatic agents.
However, polymer antistatic agents are not effective unless they are blended in a relatively large amount, and are generally more expensive than polystyrene resins, so that blending in large amounts increases the material cost of polystyrene resin sheets. It is easy to make it have the possibility of reducing the versatility of the polystyrene resin sheet.

  In order to prevent such a situation, studies have been made to effectively operate a polymer type antistatic agent in a small amount, but the method has not been established, and particularly sufficient studies have been made regarding ionomer resins. This is not a situation.

JP 2008-274031 A

  An object of the present invention is to prevent charge while reducing the blending amount of the ionomer resin in a polystyrene resin sheet containing an ionomer resin as a polymer type antistatic agent.

The present invention relating to a polystyrene-based resin sheet for solving the above-mentioned problems includes a base resin composed of at least one of general-purpose polystyrene resin (GPPS) and impact-resistant polystyrene resin (HIPS), and a polymer-type antistatic agent. A polystyrene-based resin sheet having at least a surface formed of a polystyrene-based resin composition containing an ionomer resin that is incompatible with the base resin as the polymer-type antistatic agent, and has a low density Polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polypropylene resin (PP), ethylene-vinyl acetate copolymer resin (EVA) , and poly For the base resin comprising at least one of lactic acid-based resin (PLA) When the resin component showing incompatibility is further contained in the polystyrene-based resin composition, a dispersed phase is formed in the matrix phase composed of the base resin on the surface, and the dispersed phase is The core portion is formed with a resin component and the outer shell portion is formed with the ionomer resin, and the dispersed phase contains the core shell particle having a length exceeding 1 μm. It is characterized by being.

The polystyrene-based resin sheet of the present invention is a polyolefin-based resin composition used in its formation, together with a base resin composed of at least one of general-purpose polystyrene resin (GPPS) and impact-resistant polystyrene resin (HIPS). resin, and a resin component showing the incompatibility with the base resin composed of any of polylactic acid resins are contained, the resin component is dispersed in a matrix phase consisting of the base resin Is formed on the sheet surface.
Further, the polystyrene resin sheet of the present invention contains an ionomer resin that is incompatible with the base resin as a polymer type antistatic agent in the polystyrene resin composition used for the formation, and the resin component the dispersed phase in is in the ionomer resin with the core portion is formed with Koashi E le like particles shell portion is formed is formed.
Therefore, the entire surface of the dispersed phase can be made in an excellent state of electrical conductivity, and the electrical resistance value on the surface of the polystyrene resin sheet is greatly reduced as compared with the case where only the polymer type antistatic agent is dispersed. sell.
That is, it is possible to achieve antistatic while reducing the amount of the polymer antistatic agent used.

Sectional drawing which shows the structure of the lamination sheet which concerns on 2nd embodiment. Sectional drawing which shows the structure of the lamination sheet of another aspect. The TEM image which observed the dispersion state of the ethylene-vinyl acetate copolymer (EVA) resin and polymer type antistatic agent (MK400) in a polystyrene-type resin film.

(First embodiment)
The polystyrene resin sheet of the present invention will be described below while illustrating a polystyrene resin film as the first embodiment.
First, a polystyrene resin composition for forming the polystyrene resin film will be described.

The polystyrene-based resin composition in the present embodiment includes a base resin composed of at least one of polystyrene-based resins, and a resin component that is incompatible with the base resin (hereinafter also referred to as “incompatible resin”). In addition, an ionomer resin that is incompatible with the base resin is contained as a polymer-type antistatic agent.
Note that the incompatible resin in the present embodiment is any one of a polyolefin resin, a polylactic acid resin, and an acrylic resin.
In this embodiment, by using such a material, at least the surface of the polystyrene resin film is formed with a matrix phase containing the base resin, and a dispersed phase dispersed in the matrix phase is formed. Moreover, the are the state of Koashi E le like particles outer shell is formed from an ionomer resin to form the dispersed phase with the core unit in incompatible resin is formed.
Polystyrene resin film in the present embodiment, the antistatic polystyrene based resin film while reducing the amount of the ionomer resin by which is formed the dispersed phase in the form of Koashi E Le shaped particles as described above It is illustrated.

The material for forming the matrix phase and the core portion of the dispersed phase does not have to be a single resin type, and may be composed of, for example, two or more resins that are compatible with each other.
Moreover, the ionomer resin which comprises the outer shell part of a dispersed phase can also be used in multiple combinations instead of 1 type.

In general, polymers having a solubility parameter (SP value) difference of 0.5 to 1.0 or less determined by the Fedors equation are said to be compatible with each other by approximating polarities.
On the other hand, it is said that if the SP value is further distant, it becomes incompatible.
Therefore, among the polyolefin resin, polylactic acid resin, and acrylic resin resin, those having a SP value that is significantly different from the base resin can be used to form a dispersed phase in the polystyrene resin film. .

  The polystyrene resin for constituting the matrix phase is not particularly limited. For example, styrene, α-methylstyrene, vinyltoluene, ethylstyrene, i-propylstyrene, t-butylstyrene, dimethyl Examples include homopolymers of styrene monomers such as styrene, bromostyrene, and chlorostyrene, and copolymers thereof.

  The polystyrene resin may be a copolymer of a vinyl monomer copolymerizable with the styrene monomer and the styrene monomer, and such a vinyl monomer. As, for example, alkyl (meth) acrylate such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cetyl (meth) acrylate, (meth) acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl In addition to fumarate and ethyl fumarate, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate are exemplified.

That is, even if the polystyrene resin used in the present invention is a homopolymer composed of only one of the styrene monomers exemplified above, a plurality of the various monomers exemplified above are combined. It may be a copolymer (copolymer).
Furthermore, in this embodiment, a copolymer containing a monomer other than the above monomer can be used as a polystyrene-based resin for forming a matrix phase.
Moreover, as a polystyrene resin in this embodiment, it is also possible to form a matrix phase with a plurality of homopolymers and copolymers as described above.

As the polystyrene resin used in the present invention, either an impact-resistant polystyrene resin (hereinafter also referred to as “HIPS”) or a general-purpose polystyrene resin (hereinafter also referred to as “GPPS”) is preferable.
The impact-resistant polystyrene resin (HIPS) contains a rubber component such as butadiene in addition to the styrene monomer. For example, the rubber component is copolymerized with the styrene monomer. Or a blend resin of the copolymer with another homopolymer or copolymer.
Further, the general-purpose polystyrene resin (GPPS) is a resin component excluding additives and the like substantially composed of only a styrene monomer.
Many of these polystyrene resins are commercially available, and are suitable not only because they are easily available but also relatively inexpensive.

Moreover, the said polystyrene-type resin can employ | adopt the thing whose melt flow rate (MFR) by JISK7210 (Condition H: Test temperature 200 degreeC, nominal load 5.00kg) is 20 g / 10min or less normally, 15 g / 10 min is preferable in that the antistatic effect of the ionomer resin is more easily exhibited, and the melt flow rate is particularly preferably 1 g / 10 min to 3 g / 10 min.
Polystyrene resins having a melt flow rate exceeding 20 g / 10 min generally have a low melt tension and may be unsuitable for foaming. The rate is preferably 20 g / 10 min or less.

Note that, according to the Fedors equation, a general polystyrene resin has a value of about 8.5 to 10.
Accordingly, the polystyrene resin composition contains a non-polar resin having a smaller SP value than the polystyrene resin used as the base resin or a polar resin having a larger SP value than the polystyrene resin. A dispersed phase composed of these resins can be formed in a matrix phase composed of resins.

  If the polyolefin resin is used as a resin component for forming this dispersed phase, for example, a polyethylene resin (PE), a polypropylene resin (PP), an ethylene-vinyl acetate copolymer resin (EVA), An ethylene-ethyl acrylate copolymer resin (EEA), an ethylene-methyl acrylate copolymer resin (EMA), or the like can be used.

Among these, ethylene-vinyl acetate copolymer resin (EVA) is particularly preferable in that a dispersed phase can be formed in a good dispersion state.
In particular, as EVA for forming the dispersed phase, the vinyl acetate content determined by JIS K6924-2 is preferably 3 to 30% by mass.
Moreover, it is preferable that melting | fusing point calculated | required by DSC method of JISK7121 is 60-120 degreeC.
Furthermore, the thing whose melt flow rate (MFR) calculated | required by JISK6924-2 (190 degreeC, 21.18N) is 0.2-3 g / 10min is preferable.

If a polyethylene resin (PE) is employed as the incompatible resin, for example, a high density polyethylene resin (HDPE), a medium density polyethylene resin (MDPE), a linear low density polyethylene resin (LLDPE), A low density polyethylene resin (LDPE) having a long chain branch obtained by a high pressure method can be employed.
Among the polyethylene-based resins (PE), a low density polyethylene resin (LDPE) or a high density polyethylene resin (HDPE) is preferable.

Polypropylene resin (PP) is also suitable as the incompatible resin.
As the polypropylene resin (PP), a homopolypropylene resin composed only of a propylene component, a random copolymer or a block copolymer containing an olefin component such as ethylene in addition to the propylene component can be employed.
In addition, when employ | adopting a copolymer as a polypropylene resin (PP), olefins other than a propylene are made to contain in the ratio of 0.5-30 mass% in a copolymer, Especially preferably, it is 1-10 mass%. It is desirable to use Examples of the olefin component in this case include ethylene or an α-olefin having 4 to 10 carbon atoms.
In particular, a high melt tension polypropylene-based resin is preferable. For example, those described in Japanese Patent No. 2521388 can be suitably used.

  Further, when the polylactic acid resin (PLA) is used as a resin component for forming the dispersed phase, for example, poly D-lactic acid resin, poly L-lactic acid resin, poly D-lactic acid and poly L- Poly DL-lactic acid resin which is a copolymer with lactic acid, a mixture of poly D-lactic acid resin and poly L-lactic acid resin (stereo complex), a copolymer of poly D-lactic acid and hydroxycarboxylic acid, poly L- Copolymers of lactic acid and hydroxycarboxylic acid, and copolymers of poly D-lactic acid or poly L-lactic acid, aliphatic dicarboxylic acid and aliphatic diol can be employed.

Further, when the acrylic resin is used as a resin component for forming the dispersed phase, for example, (meth) acrylic acid, (meth) acrylic acid ester, (meth) acrylamides, and (meth) acrylonitrile Can be used as a main monomer component.
The term “(meth) acryl” is used in the present specification to include both “methacryl” and “acryl”.

  More specifically, monomers (monomer components) constituting the acrylic resin include acrylic acid, methacrylic acid: acrylic acid ester or methacrylic acid ester: for example, methyl acrylate, ethyl acrylate, acrylic acid n -Propyl, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, acrylic acid Alkyl acrylates having 1 to 18 carbon atoms in the alkyl group such as palmityl or cyclohexyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, ethyl methacrylate Alkyl groups such as butyl, t-butyl methacrylate, hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, palmityl methacrylate and cyclohexyl methacrylate have 1 to 1 carbon atoms. Examples include about 18 methacrylic acid alkyl esters.

  Furthermore, as a monomer component constituting the acrylic resin, (meth) acrylic acid such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, etc. An alkyl ester having a hydroxyl group in the side chain of the (meth) acrylic acid side chain such as methoxybutyl acrylate, methoxybutyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate, ethoxybutyl acrylate, ethoxybutyl methacrylate, etc. Alkyl ester having alkoxyl group; Alkenyl ester of (meth) acrylic acid such as allyl acrylate and allyl methacrylate; allyloxyethyl acrylate and allyloxyethyl methacrylate Alkenyloxyalkyl esters of (meth) acrylic acid such as glycidyl acrylate, glycidyl methacrylate, and alkyl esters having an epoxy group in the side chain of acrylic acid such as methyl glycidyl acrylate and methyl glycidyl methacrylate; diethylamino acrylate Mono- or di-alkylaminoalkyl esters of (meth) acrylic acid such as ethyl, diethylaminoethyl methacrylate, methylaminoethyl acrylate, methylaminoethyl methacrylate; silyl group, alkoxysilyl group or hydrolyzable alkoxy as side chain Examples include silicone-modified (meth) acrylic acid esters having a silyl group.

  In addition, examples of the monomer component constituting the acrylic resin include acrylamides or methacrylamides: for example, acrylamide; methacrylamide; (meth) acrylamide having a methylol group such as N-methylolacrylamide and N-methylolmethacrylamide; N (Meth) acrylamide having an alkoxymethylol group such as alkoxymethylolacrylamide (for example, N-isobutoxymethylolacrylamide) and N-alkoxymethylolmethacrylamide (for example, N-isobutoxymethylolmethacrylamide); N-butoxy Examples thereof include (meth) acrylamide having an alkoxyalkyl group such as methyl acrylamide and N-butoxymethyl methacrylamide.

  In addition, various acrylic monomers such as acrylonitrile and methacrylonitrile can be cited as monomer components constituting the acrylic resin.

Even if the acrylic resin in the present embodiment is a homopolymer composed of only one of the various monomer components exemplified above, a copolymer (co-polymer) formed by combining a plurality of the various monomer components exemplified above. Polymer).
Furthermore, in this embodiment, a copolymer containing another monomer component in addition to the monomer component can be used as the acrylic resin.

  The monomer component other than those exemplified above is not particularly limited as long as it forms a copolymer with the monomer component. For example, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl lactate, vinyl butyrate, versatic acid Examples thereof include vinyl monomers such as vinyl and vinyl benzoate, butadiene, and styrene.

  As the acrylic resin in the present embodiment, polymethyl methacrylate resin (PMMA) is preferable, and PMMA is also preferable because it is easy to obtain an inexpensive commercial product.

The ionomer resin for enclosing the dispersed phase formed by the incompatible resin as described above to form the outer shell portion of the core-shell-like particle is not particularly limited as long as it is incompatible with the base resin. However, potassium ionomer of ethylene / unsaturated carboxylic acid copolymer is preferable, and potassium ionomer of ethylene- (meth) acrylic acid random copolymer is particularly preferable.
As such an ionomer resin, for example, commercially available products from Mitsui DuPont Polychemical Co., Ltd. under the trade name “ENTILA MK400” and the trade name “ENTILA SD100” can be employed.

  Whether or not it is incompatible with the base resin can be predicted based on the Fedors equation as described above. For example, commercially available resins such as incompatible resins and ionomer resins If it is difficult to accurately calculate the solubility parameter value because the molecular structure cannot be specified sufficiently, the resin can be obtained by actually melting and mixing the resins together and cooling. The dispersion state of each sample can be judged by directly observing with a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

The blending ratio of the base resin and the incompatible resin in the polystyrene resin composition of the present embodiment, the content of the ionomer resin, etc. are not particularly limited, but the surface resistivity of the polystyrene resin film is Since any one of 1 × 10 ⁸ Ω / □ to 1 × 10 ¹³ Ω / □ is preferable, among those capable of imparting such a surface resistivity to a polystyrene-based resin film, the ionomer resin is more It is preferable to select a blending ratio that can reduce the content.
The surface resistivity of the polystyrene resin film, 1 × 10 ⁹ Ω / □, more preferably to a ~1 × 10 ¹² Ω / □ ^{either, 1 × 10 9 Ω / □} ~1 × 10 11 Ω / Most preferably, any one of □ is used.
In the point which can give reliably the value of such a surface resistivity with a polystyrene-type resin film, normally the ratio of the incompatible resin which occupies for all the resin components of a polystyrene-type resin composition shall be 5-20 mass%. It is preferable to set it to any one of 5 to 15% by mass.

Moreover, the said ionomer resin is normally contained so that the ratio which occupies for all the resin components of a polystyrene-type resin composition may be either in 1-30 mass%.
The lower limit value of the ionomer resin is 1% by mass because, in the case of a content less than this, there is a possibility that a sufficient antistatic effect may not be exerted on the polystyrene resin film, The upper limit is set to 30% by mass. Even if an ionomer resin is contained exceeding this, not only the antistatic effect corresponding to the content is difficult to be obtained but also the material cost of the polystyrene resin film is increased. This is because there is a risk of losing.
From this point of view, the ionomer resin is preferably contained so that the proportion of all the resin components of the polystyrene resin composition is 3 to 20% by mass. It is particularly preferable that the content is 15% by mass.

In addition, you may contain polymeric antistatic agents other than ionomer resin with the said ionomer resin.
In order to further improve the antistatic effect, for example, an anionic surfactant such as sodium dodecylbenzenesulfonate, other surfactant, or a low molecular weight antistatic agent such as an alkali metal salt is used in combination. May be.
However, since the amount of eluted ions may increase with the addition of these low molecular weight antistatic agents, the low molecular weight antistatic agent is an antistatic agent contained in the polystyrene resin composition (high molecular charge). (Inhibitor + low molecular type antistatic agent) It is preferable that the total amount of the additive is less than 0.5% by mass.

  Although not described in detail here, the polystyrene resin composition used for forming the polystyrene resin film of the present embodiment can contain a compounding agent used for forming a general polymer film, for example, Various stabilizers such as weathering agents and anti-aging agents, processing aids such as lubricants, slip agents, antifogging agents, pigments, fillers and the like can be appropriately added as additives.

Next, a production method for producing a polystyrene resin film using such a polystyrene resin composition will be described.
In the present embodiment, a method used in a general film manufacturing method can be employed. For example, a resin kneading for producing a compound containing the base resin, the incompatible resin, the ionomer resin, and the like. After carrying out the process, a method of carrying out an extrusion process in which the obtained compound is extruded into a film can be adopted.
Below, each process is demonstrated more concretely.

(Resin kneading process)
First, after dry blending with a tumbler blender, Henschel mixer, etc. after measuring the base resin, incompatible resin, polymer antistatic agent, and if necessary, additives such as slip agent and antifogging agent In a single screw extruder, a multi-screw extruder, a kneader, a Banbury mixer, etc., each compounded material is melt-kneaded so as to be in a substantially uniformly mixed state.
Thereafter, the kneaded product is extruded into a strand shape and pelletized, or hot cut and pelletized to produce a compound pellet made of a polystyrene resin composition.

(Extrusion process)
As a method of extruding the compound pellet obtained in the resin kneading step into a film in a hot melt state, for example, it is extruded from a circular die or the like to form a film by an inflation method, or is extruded from a T-die or the like by a cast method There is a method of making it into a film.
Of these, a flat die such as a T-die is easy to stretch in the extrusion direction, but requires a facility such as a tenter for stretching in the width direction. It is preferable to carry out an extrusion process using a die.

At the time of mixing in the heat-melted state in the kneading step and the extrusion step, for example, if a polystyrene resin composition containing a polystyrene resin (GPPS) as a base resin and LDPE as the incompatible resin is produced, the polarity is polar. LDPE having a low density shows incompatibility with the polystyrene-based resin, and the LDPE is dispersed in GPPS.
That is, a sea-island structure in which a dispersed phase is formed by LDPE is formed in the molten resin composition.
At this time, the ionomer resin that is incompatible with GPPS gathers at the interface between the dispersed phase and the matrix phase to form a region with low electrical resistance along the interface.
That is, LDPE is dispersed in GPPS, which is a base resin, in a state of being covered with a polymer type antistatic agent.

In addition, the core-shell-shaped particles in which the LDPE is used as a core and the outer shell portion is formed of an ionomer resin are aligned along the resin flow direction (extrusion direction) due to the shearing force acting on the molten resin composition in the extrusion process. It extends for a long time and has a relatively high aspect ratio to form a dispersed phase.
And the state which this disperse phase extended long is maintained also in the resin film obtained by cooling the resin composition of a molten state, flowing in the said extrusion process.
By this, for example, the surface resistivity can be remarkably lowered by forming elongated particles exceeding 1 μm in the dispersed phase.

To explain this, an ionomer resin is a polymer excellent in conductivity expression, and it imparts conductivity to the surface of the resin film to reduce the surface resistivity to prevent antistatic. When the ionomer resin is dispersed in a polystyrene resin to produce a polystyrene resin film, the ionomer resin is granulated and dispersed in the polystyrene resin film.
At this time, the surface resistivity of the polystyrene resin film is influenced by the area ratio of the ionomer resin particles in the surface area and the interparticle distance of the ionomer resin particles.
That is, the surface resistivity can be lowered as the area ratio of the ionomer resin particles occupying the surface of the polystyrene resin film is larger and the distance between the ionomer resin particles is shorter.

However, when the ionomer resin is dispersed alone in the polystyrene resin as described above, the ionomer resin is dispersed as fine dot-like particles, and the amount that can bring the distance between the particles close to some extent. If not contained, the effect of reducing the surface resistivity is not exhibited.
Here, in the present embodiment, resin particles are formed in which the core portion is formed of resin particles incompatible with the polystyrene-based resin, and the outer shell portion (shell portion) is formed of an ionomer resin.
From this, the surface of the core-shell-like resin particles can be effectively used for the expression of conductivity, and the area ratio of the resin particles on the surface of the polystyrene resin film can be increased while suppressing the use amount of the ionomer resin. At the same time, the distance between the resin particles can be made closer.

  Moreover, the particles forming the dispersed phase extend long along the flow direction (extrusion direction) of the resin, and the length in the film plane direction exceeds 1 μm. In addition to reducing the electrical resistance value, the electrical resistance value can also be reduced in the direction intersecting the longitudinal direction of the particles.

That is, in the polystyrene-based resin film of the present embodiment, since the dispersed phase is formed in a long and thin granular shape along the resin flow direction, a section in which the particles are adjacent to each other is formed long, and the electric resistance value therebetween. There is a high possibility that a low point will be formed.
Therefore, the electrical resistance value can be reduced in directions other than the resin flow direction, which is advantageous in terms of conductivity, and the surface resistivity of the polystyrene resin film is suppressed while suppressing the blending amount of the polymeric antistatic agent. Can be lowered to a value of 10 ¹³ (Ω / □) order or less (less than 1 × 10 ¹⁴ ) which is generally required.

  The effects as described above are manifested when the ionomer resin employed as the polymer antistatic agent exhibits incompatibility with the base resin forming the matrix phase. It is more prominently expressed by showing incompatibility with the incompatible resin forming the part.

In addition, as a specific method for forming the core-shell-like particles having the outer shell portion formed of such an ionomer resin to be longer than 1 μm as described above, there is a method of adjusting how shear is applied during extrusion. .
The size of the dispersed phase can also be directly confirmed by SEM or TEM. For example, the size of the dispersed phase is randomly selected at a magnification of several thousand times to several tens of thousands times with respect to a sample collected from the surface portion of the polystyrene resin film. If a particle having a length of 1 μm or more can be confirmed in more than half of the fields of view, it can be determined that a dispersed phase of 1 μm or more is formed on the polystyrene resin film.
Note that the shape and size of the dispersed phase inside the film does not have a great influence on the antistatic performance, so such a dispersed phase may be formed at least on the surface of the polystyrene resin film.

  As described above, it is possible to reduce the surface resistivity while further suppressing the amount of the ionomer resin used in the polystyrene resin film by adjusting the shape to a predetermined shape as well as simply forming the core-shell particles. .

In addition, as shown above, in the polystyrene resin film of the present embodiment, since the electric resistance value can be reduced particularly in the direction of the longitudinal direction of the polystyrene resin particles, the polystyrene resin When the film is formed into a long shape by continuous extrusion and wound into a roll shape, a more remarkable effect is exhibited.
In other words, a resin film wound up in a roll shape is usually used with the outer film pulled out, and it tends to generate static electricity when the drawn film leaves the back of the film that is in contact with the inner film. The polystyrene resin film of the embodiment is in a state in which polystyrene resin particles extend long in the roll winding direction, and the electrical resistance value in this direction is particularly reduced. Is generated, it is easy to move toward the place where the films are in contact with each other, which is opposite to the direction in which the charge is drawn out, and it is easy to achieve electrical neutralization.
Thus, the polystyrene-based resin film of this embodiment not only exhibits excellent antistatic properties when processed into a product such as a container, but also excellent in the state of an intermediate product such as a film roll. The effect is demonstrated.

(Second embodiment)
Next, a laminated sheet will be described as a second embodiment of the present invention.
FIG. 1 is a cross-sectional view of a laminated sheet according to the present embodiment. As shown in FIG. 1, the laminated sheet 1 according to the present embodiment is polystyrene that forms the surface layer of the laminated sheet 1. And a foamed layer 20 laminated in a state of adhering to the polystyrene resin film layer 10 on the back side.

The polystyrene resin film layer 10 is formed using the polystyrene resin composition described in the first embodiment, and an ionomer resin that is incompatible with the polystyrene resin is used as the polymer antistatic agent. It is formed by using a polystyrene-based resin composition containing an incompatible resin among a polyolefin-based resin, a polylactic acid-based resin, and an acrylic resin.
That is, as for the lamination sheet 1, the surface layer is formed by the polystyrene-type resin film layer 10 with low surface resistivity, and antistatic is achieved.

On the other hand, the resin composition used for forming the foamed layer 20 is not particularly limited, and even if it is a resin composition formulated to be antistatic like the polystyrene resin film layer 10, The resin composition in which such prescription is not made may be used.
For example, the foamed layer 20 is formed by adding a thermal decomposition type foaming agent to a base resin containing at least one of polystyrene-based resins, or by adding a gas regulator to gas foam. obtain.

Examples of the heat decomposable foaming agent include azodicarbonamide, sodium hydrogen carbonate, a mixture of sodium hydrogen carbonate and citric acid, and the like.
Examples of the air conditioner include talc, mica, silica, diatomaceous earth, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, and carbonic acid. Examples thereof include inorganic compounds such as magnesium, potassium sulfate, barium sulfate, and glass beads, and organic compounds such as polytetrafluoroethylene.
Furthermore, in gas foaming, hydrocarbons such as butane and pentane can be employed as a foaming agent.
These can be used alone or in combination for forming the foamed layer 20.

The term “polystyrene resin film layer” is used because the foamed layer 20 is formed in a non-foamed state in the form of a film while the foamed layer 20 is in a foamed state as described above. However, the present invention is not limited to the case where it is formed by a polystyrene-based resin film prepared separately from the foam sheet for forming the foam layer.
Therefore, as the laminated sheet of the present embodiment, the polystyrene resin film for forming the polystyrene resin film layer 10 and the foamed sheet for forming the foam layer 20 are once prepared separately, and then In this case, a polystyrene resin film layer and a foamed layer formed at the same time by a coextrusion molding method can be used instead. is there.

Moreover, the coextrusion molding method is superior to a method such as heat lamination in that it is easy to form the polystyrene-based resin film layer 10 having antistatic properties uniformly and thinly.
In particular, as a method for producing the laminated sheet 1 according to the present embodiment, it is preferable to adopt a coextrusion molding method by a feed block method.

As such a coextrusion molding method, for example, a method described in JP-A-6-238788 can be employed.
That is, after using different extruders for extruding the polystyrene-based resin film layer 10 having antistatic performance and for extruding the foamed layer 20, the molten resin composition extruded from these is joined to one die, For example, the resin composition for forming the foam layer is extruded along the inner side of the circular die and the resin composition for forming the polystyrene-based resin film layer is extruded along the outer side to form two layers inside and outside. By carrying out the extrusion, a cylindrical laminated sheet 1 in which the polystyrene-based resin film layer 10 is formed on the outside and the foam layer 20 is formed on the inside can be formed.

  Also in this laminated sheet 1, a dispersion state of an incompatible resin similar to the polystyrene resin film of the first embodiment is formed in the polystyrene resin film layer 10, and an ionomer is formed at the interface between the incompatible resin and the base resin. Since the resin is collected, an excellent antistatic property is exhibited while the amount of the ionomer resin used is small.

In addition, in this 2nd embodiment, although the laminated sheet of the two-layer structure of the polystyrene-type resin film layer 10 and the foaming layer 20 is illustrated, for example, when it has a some film layer as shown in FIG. In addition, the case of having a plurality of foamed layers is also within the intended scope of the present invention.
For example, the polystyrene resin film layers 10 and 10 ′ are provided on both surfaces of the foam layer 20 (FIG. 2A), or a plurality of layers are provided between the two polystyrene resin film layers 10 and 10 ′ constituting both surfaces. In the case where the foamed layers 20 and 20 ′ are provided (FIG. 2 (b)), the range is intended as the laminated sheet of the present invention.
Furthermore, the case where two polystyrene resin film layers 10 and 10 ″ are provided on one side of the foam layer 20 (FIG. 2C) is also within the intended range of the present invention.
In addition, two or more polystyrene-based resin film layers can be formed not only on one side of the foam layer but also on both sides. Not limited to these, various laminated structures can be formed on the laminated sheet.
In addition, as shown in FIGS. 2 (a) and 2 (b), when a polystyrene resin film layer is provided on both sides, it is only necessary to provide antistatic performance only on the necessary side. One or both of the polystyrene resin film layers can be formed of a polystyrene resin composition containing an incompatible resin and an ionomer resin.
2C, when two polystyrene resin film layers are provided on one side of the foam layer 20, only the outer polystyrene resin film layer 10 or the outer polystyrene resin film layer 10 is provided. And the inner polystyrene resin film layer 10 "can be formed of a polystyrene resin composition containing an incompatible resin and an ionomer resin.

(Third embodiment)
In order to form a foamed sheet as the polystyrene resin sheet of the present invention, it can be produced in the same manner as the foamed layer of the laminated sheet.
That is, it is possible to employ a method in which an ionomer resin is contained together with an incompatible resin, and a polystyrene resin composition further containing a component for forming bubbles is extruded and foamed with an extruder and molded into a sheet.
Also in this case, the polystyrene-based resin of the first embodiment is formed by forming a dispersed phase on the surface of the foamed sheet by the core-shell-like particles in which the incompatible resin forms the core portion and the ionomer resin forms the outer shell portion. Like the film or the laminated sheet of the second embodiment, a foamed sheet excellent in antistatic performance can be produced while suppressing the amount of ionomer resin used.

The polystyrene-based resin film of the first embodiment, the laminated sheet of the second embodiment, and the foamed sheet are suitable for general consumer materials because the amount of ionomer resin used is suppressed and the material cost is reduced. In particular, since contamination during storage such as dust adhesion is suppressed, it is suitable for food applications.
For example, the laminated sheet and foamed sheet of the second embodiment can be suitably used as a raw material sheet such as a food tray because it is lightweight and high in strength, and has excellent heat insulation performance and suppresses contamination during storage. .

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Combination agent)
Below, the abbreviation of the compounding agent used for preparation of the polystyrene-type resin film of each Example and a comparative example, and the detail are described.

(Evaluation 1)
Polystyrene resin films were prepared according to the formulations shown in Table 1 below (Formulations 1 to 8).
Moreover, the value of the surface resistivity was measured with respect to the obtained polystyrene resin film by the method described in JIS K 6911: 1995 “Thermosetting Plastics—General Test Method”.
Specifically, after a flat square test piece having a side of 10 cm is left in an atmosphere of a temperature of 22 ° C. and a humidity of 60% for 24 hours, a test apparatus (manufactured by Advantest Corporation) under an environment of a temperature of 22 ° C. and a humidity of 60% is used. Using a digital ultra-high resistance / microammeter R8340 and a resiliency chamber R12702A), an electrode is crimped to a test piece with a load of about 30 N, a voltage of 500 V is applied, and a resistance value after one minute has elapsed. Measured and calculated by the following formula.
ρs = π (D + d) / (D−d) × Rs
However,
ρs: Surface resistivity (Ω / □)
D: Inner diameter (cm) of the annular electrode on the surface (7 cm for the resiliency chamber R12702A)
d: outer diameter (cm) of inner circle of surface electrode (5 cm for resiliency chamber R12702A)
Rs: Surface resistance (Ω)

Moreover, measurement was implemented 3 times and each arithmetic mean value was calculated | required.
The results are also shown in Table 1.

As described above, it can be seen that the surface resistivity value can be lowered by simply adding an ionomer resin to GPPS by including a resin component that is incompatible with GPPS such as LDPE, PMMA, and PLA as described above. .
Further, the effect of decreasing the surface resistivity by the addition of the ionomer resin is more remarkable in “HRM18” and “HRM40” having an MFR of 15.0 g / 10 min or less than “679” having an MFR exceeding 18.0 g / 10 min. This can also be seen from the results in Table 1 above.
In addition, the surface resistivity of the film made of only “HRM40” to which no antistatic agent is added is 5.3 × 10 ¹⁵ (Ω / □), and the surface resistivity of the film of “HRM18” is 4. 8 × a 10 ¹⁵ (Ω / □), the surface resistivity of the film of "679" is ^{5.8 × 10 15 (Ω / □} ).

The surface resistivity of the mixed resin film of 90% by mass of “HRM26” (GPPS, MFR = 1.4 g / min) and 10% by mass of “MK400” was measured to be 3.3 × 10 ¹⁰ (Ω / □ )Met.
Similarly, when the surface resistivity of a mixed resin film of 90% by weight of “679” (GPPS, MFR = 18.0 g / min) and 10% by weight of “MK400” was measured, 1.7 × 10 ¹¹ (Ω / □) Met.
Also from this evaluation result, the effect of decreasing the surface resistivity by the addition of the ionomer resin is more remarkable in “HRM26” having an MFR of 15.0 g / 10 min or less than “679” having an MFR of more than 15.0 g / 10 min. I found out.

(Evaluation 2)
Polystyrene resin films were prepared according to the formulations shown in Table 2 below (compounds 9 to 14).
Moreover, the value of surface resistivity was measured with respect to the obtained polystyrene-type resin film similarly to previous evaluation 1.
The results are also shown in Table 2.

Also from the above table, by including a resin component that is incompatible with GPPS such as EVA, LDPE, HDPE, PP, the value of the surface resistivity is decreased more than simply including the ionomer resin in GPPS. I can understand.
In addition, the addition of an ionomer resin alone makes it possible to obtain antistatic performance by further adding a resin component exhibiting incompatibility even in an addition amount that cannot obtain the generally required antistatic performance. You can see that

(Evaluation 3)
Polystyrene resin films were prepared according to the formulations shown in Table 3 below (formulations 15 to 18).
Moreover, the value of surface resistivity was measured with respect to the obtained polystyrene-type resin film similarly to previous evaluation 1.
The results are also shown in Table 3.

  From the above table, it can be seen that the greater the amount of EVA (LV115) added, the lower the surface resistivity value can be.

(Evaluation 4)
Polystyrene resin films were prepared according to the formulations shown in Table 4 below (Formulations 19 to 23).
Moreover, the value of surface resistivity was measured with respect to the obtained polystyrene-type resin film similarly to previous evaluation 1.
The results are also shown in Table 4.

It can be seen from the above table that the amount of ionomer resin added is at least 1% by mass.
Moreover, it turns out that an antistatic effect is exhibited more notably by including an ionomer resin in the ratio which will be 4 mass% or more in the resin component in a polystyrene-type resin film.

(Evaluation 5)
Polystyrene resin films were prepared according to the formulations shown in Table 5 below (formulations 24 to 27).
Moreover, the value of surface resistivity was measured with respect to the obtained polystyrene-type resin film similarly to previous evaluation 1.
The results are also shown in Table 5.

  From the above table, it can be seen that an impact-resistant polystyrene resin (HIPS) is also effective as a polystyrene-based resin that is a base resin.

(Evaluation 6)
Polystyrene resin films were prepared according to the formulations shown in Table 6 below (formulations 27 to 29).
Moreover, the value of surface resistivity was measured with respect to the obtained polystyrene-type resin film similarly to previous evaluation 1.
The results are also shown in Table 6.

  From the results shown in Table 6 above, it can be seen that the same effect is exhibited even in an ionomer resin different from the previous evaluation.

(TEM observation)
A polystyrene resin film extruded with a polystyrene resin composition containing 65% by mass of “HRM18” (GPPS), 27% by mass of “LV115” (EVA), and 8% by mass of “MK400” (ionomer resin) is used. FIG. 3 shows a state in which the thin piece sample prepared in this manner was observed with a transmission electron microscope (TEM).
FIG. 3 also shows that EVA forms a dispersed phase having a high aspect ratio, and an ionomer resin, which is a polymer-type antistatic agent, gathers around it to form an outer shell.
This also shows that according to the present invention, it is possible to achieve antistatic while reducing the amount of the polymeric antistatic agent used in the polystyrene resin sheet.

Note that the test piece in the TEM observation is a slice of a polystyrene resin film along the extrusion direction, and the TEM image in FIG. 3 is the sliced test piece on the side corresponding to the surface of the polystyrene resin film. Is observed.
That is, the state in the vicinity of the surface side in the cross section in the thickness direction of the polystyrene resin film is observed from the direction orthogonal to the extrusion direction.

  1: Laminated sheet, 10: Polystyrene resin film layer, 20: Foam layer

Claims (5)

At least the surface is formed by a polystyrene resin composition containing a base resin composed of at least one of general-purpose polystyrene resin (GPPS) and impact-resistant polystyrene resin (HIPS) and a polymer-type antistatic agent. A polystyrene resin sheet,
As the polymer-type antistatic agent, an ionomer resin which is incompatible with the base resin is contained, and low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene ( LLDPE), a polypropylene resin (PP), an ethylene-vinyl acetate copolymer resin (EVA), and a resin component that is incompatible with the base resin comprising at least one of polylactic acid resin (PLA) Is further contained in the polystyrene-based resin composition, so that a dispersed phase is formed in the matrix phase composed of the base resin on the surface, and the dispersed phase forms a core portion with the resin component. And core-shell particles having an outer shell formed of the ionomer resin, and the dispersed phase Polystyrene resin sheet, characterized in that it contains the said core-shell particles whose length exceeds 1μm is.   The polystyrene resin sheet according to claim 1, wherein the base resin has a melt flow rate of 15 g / 10 min or less according to JIS K 7210 condition H (test temperature: 200 ° C, nominal load: 5.00 kg).   The polystyrene resin sheet according to claim 1 or 2, wherein the polystyrene resin sheet is a film in which the polystyrene resin composition is used. The polystyrene resin sheet according to claim 1 or 2, wherein the polystyrene resin sheet is a foamed sheet using the polystyrene resin composition.   3. The laminate sheet according to claim 1, wherein the laminate sheet is provided with a polystyrene resin film layer formed of the polystyrene resin composition as a surface layer, and further includes a foam layer laminated on the back side of the surface layer. Polystyrene resin sheet.