JP2019064726A - Transparent polyolefin resin cup - Google Patents

Abstract

To provide a cup exhibiting excellent transparency and excellent low temperature impact resistance.SOLUTION: There is provided a transparent polyolefin resin cup satisfying the following characteristics. (1) A crystal nucleating agent or layered silicate of 300 ppm or more is contained. (2) The cup has a thickness of 100 μm or more, and a cup side face has a haze of 15% or less. (3) When measuring melting temperature of the cup side face by a melting temperature measuring method specified by JIS K6922-2, first melting temperature Tm1 and second melting temperature Tm2 satisfy the following relationship Tm1-Tm2≥0.5°C.SELECTED DRAWING: None

Description

The present invention relates to a transparent polyolefin resin cup containing a nucleating agent and the like.

  Containers for containing food etc. are often light in weight, easy to mold such as cups, excellent in productivity, and relatively inexpensive, and containers made of resin are often used. Furthermore, transparent resin is used for applications that require visual visibility of the contents, and resins that are excellent in impact resistance are used for applications that do not break even if dropped.

  In recent years, in convenience stores and the like, a style in which coffee ground in a store is put in a cup and consumed is popular, and a resin container is also used for the cup into which the coffee is inserted. Among them, for iced coffee, a transparent cup is preferred and a transparent resin is used. In the past, after receiving an order at a store, ice was put in a cup and coffee was poured, so transparency and heat resistance around boiling water were required, but ice was put in the cup in advance to reduce the load at the store. It becomes a type sealed with a sealing material and becomes freezer preservation, and low temperature impact resistance has come to be required. Furthermore, in the factory, ice is put into a cup and frozen and transported by low temperature, and further low temperature impact characteristics are required.

  Although impact-resistant polystyrene was originally used, although it is transparent, there is a problem in low-temperature impact resistance. Impact-resistant polyethylene, acrylic and polycarbonate are non-crystalline resins and are inherently transparent but are inferior in impact resistance below the glass transition temperature, and often have low-temperature impact resistance due to the presence of a glass transition temperature near room temperature There are many.

  Next, polypropylene is excellent in impact resistance at normal temperature, and in particular polypropylene block copolymer is excellent in impact resistance up to around -5 ° C, but the polypropylene phase and the polyethylene phase have a sea-island structure, and their respective refractions Poor transparency due to different rates. Random polypropylene is excellent in transparency because it does not have a layer structure, but the impact resistance at around 0 ° C. is drastically reduced because there is no shock absorption capability due to the sea-island structure. From this, many studies on resins that are compatible with low temperature impact resistance and transparency have been conducted.

  Therefore, transparency is imparted by blending polypropylene and ethylene copolymer rubber with polypropylene block resin and finely dispersing polyethylene of island layer of sea-island structure. Polyethylene is very excellent in low-temperature impact because it has a very low glass transition temperature, but is inferior in transparency, it is extremely opaque in the density region of rigid polyethylene required for cups, and research has been conducted to impart transparency conventionally Many have been done.

  Many attempts have been made to add inorganic salts, carboxylates, nucleating agents and the like to polyethylene.

  Addition of lithium carbonate, addition of basic 12-hydroxy magnesium stearate and zinc 12-hydroxy stearate mixture, combination of antioxidant and antiblocking agent, addition of layered silicate, addition of kaolin, addition of nucleating agent Transparency is improved by (see, for example, Patent Documents 1 to 6). On the other hand, transparency is improved by adding polyethylene cross-linked by gamma rays (see, for example, Patent Document 7). On the other hand, there is a method of enhancing the transparency by rolling a polyethylene sheet, rod, molded article and the like once molded (see, for example, Patent Documents 8 to 12). Furthermore, there is a method of imparting transparency by drawing and stretching a polyethylene sheet, a rod, a molded article, etc. which has been molded once (see, for example, Patent Documents 13 and 14).

Unexamined-Japanese-Patent No. 7-109387 Japanese Patent Laid-Open No. 7-126447 Japanese Patent Application Laid-Open No. 9-40815 Japanese Patent Application Laid-Open No. 11-293055 JP 2000-109623 A Unexamined-Japanese-Patent No. 2014-19733 Japanese Patent Application Laid-Open No. 9-31256 Japanese Patent Application Laid-Open No. 62-64846 Japanese Patent Application Laid-Open No. 62-122735 Unexamined-Japanese-Patent No. 2-143837 JP, 2009-149816, A JP, 2013-116938, A JP-A-8-134284 JP-A-2010-510094

  As mentioned above, development of a cup for coffee beverages which can be transported by freezing and has transparency has been demanded. The problem required for the resin is a thermoplastic resin capable of vacuum forming or press forming a cup from a sheet, having transparency, and excellent drop impact resistance at a low temperature of -30.degree. C., for example. In addition, when a coffee cream is added, adhesion of milk components and deposition of odor are observed in the PET resin.

  As described above, there is no material having no milk component adhesion and transparency and excellent in low temperature impact resistance in the past, and improvement of transparency or improvement of low temperature impact resistance has been performed. Although there is polyethylene as a material excellent in low-temperature impact resistance, it is inferior in transparency and opaque in high-density polyethylene which is required to have rigidity. Although the improvement of transparency by adding a nucleating agent etc. to polyethylene has been performed, it does not reach the improvement to the area of high transparency required for a product.

  Moreover, the improvement of transparency by adding polyethylene cross-linked by gamma rays is also seen to have a certain effect, but it is inferior in productivity due to the gamma ray irradiation process, and there is a risk of generation of odor due to decomposition of polyethylene by gamma rays. is there.

  On the other hand, there is a method to increase the transparency by rolling the polyethylene sheet, rod, molded product etc. once molded, but there is a compression process with rolling rolls, so the production speed is very slow and the productivity is inferior Low and difficult to apply to the shape of the cup. In addition, there is a problem that transparency is lost and whitening occurs when the drawn sheet is reheated, melted and shaped because of cup shaping. Furthermore, it is known that transparency is exhibited in a film or fiber by rolling or tension, but it is limited to a thin film or thread-like shape and can not be applied to a shape like a cup.

  On the other hand, polypropylene is relatively easy to develop transparency but inferior in low temperature impact resistance. Although block polypropylene (PP) having a rubber component in the resin is often used to improve impact resistance, it is still insufficient in low-temperature impact resistance as well as inferior in transparency. In addition, special rubber components are often added as a compatibilizer for micro-dispersion of the rubber components in the resin, but the low temperature impact resistance at -30 ° C is still insufficient. Polyethylene terephthalate resin (PET) is known to exhibit transparency when stretched by biaxial stretching etc. However, with so-called amorphous PET, shrinkage when hot water is put in is a problem, and partially crystallized The PET-G, which has enhanced heat resistance, is excellent in transparency and low-temperature impact resistance. However, since PET resin has polar groups in the resin, the deposition of milk components causes problems with product clouding and odor deposition.

  On the other hand, when rolling or drawing polyethylene, there is a composition that can not necessarily exhibit transparency, and since it shows non-uniform elongation when it is subjected to tensile drawing, the transparent and opaque parts are mixed in the product itself to give an appearance. I'm hurt.

  Then, an object of the present invention is to provide a thermoplastic resin cup excellent in transparency and excellent in low-temperature impact resistance.

  As a result of intensive studies to solve the above problems, the inventors of the present invention include a crystal nucleating agent or a layered silicate, the thickness of the cup is 100 μm or more, and the haze on the side of the cup is 15% or less. It has been discovered that it is possible to obtain a thermoplastic resin cup which is extremely transparent and excellent in low temperature impact resistance by having a specific melting temperature characteristic, and to make the present invention.

That is, the present invention
[1]
Transparent polyolefin resin cup meeting the following characteristics.
(1) A crystal nucleating agent or layered silicate containing 300 ppm or more (2) The thickness of the cup is 100 μm or more and the haze on the side of the cup is 15% or less (3) Melting temperature specified in JIS K6922-2 When the melting temperature of the cup side is measured by the method of measurement, the first melting temperature Tm1 and the second melting temperature Tm2 satisfy the following relationship: Tm1-Tm2 ≧ 0.5 ° C.
[2]
The transparent polyolefin resin cup according to [1], wherein the transparent polyolefin resin contains a high density polyethylene resin, and the density measured by a method prescribed in JIS K7112 is 935 kg / m ³ or more.
[3]
The molded article is extruded according to the method of ISO1133 against the density D1 of the side of the cup measured according to the method D defined in JIS K7112, and the density D2 measured according to the method of JIS K7112 satisfies the following relationship. Polyolefin resin cup.

D1-D2 ≧ 0.5 kg / m ³
[4]
The transparent polyolefin resin cup according to [2] or [3], wherein the transparent polyolefin resin comprises a polyethylene resin polymerized by a chromium catalyst.
[5]
The transparent polyolefin resin cup according to [2] or [3], wherein the transparent polyolefin resin comprises a low density polyethylene resin polymerized by a high pressure method.
[6]
The transparent polyolefin resin cup according to any one of [1] to [5], wherein the total absorbed energy in a drop impact test at -30 ° C for the side surface of the cup is 2 J or more.

  The cup of the present invention is excellent in transparency and excellent in low temperature impact resistance.

  Hereinafter, modes for carrying out the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail below. In addition, this invention is not limited to the following embodiment, It can variously deform and implement within the range of the summary.

The transparent polyolefin resin cup of the present embodiment satisfies the following characteristics.
(1) Containing 300 ppm or more of crystal nucleating agent or layered silicate.
(2) The thickness of the cup is 100 μm or more, and the haze on the side of the cup is 15% or less.
(3) When the melting temperature of the cup side surface is measured by the method of measuring the melting temperature specified in JIS K6922-2, the first melting temperature Tm1 and the second melting temperature Tm2 satisfy the following relationship.

Tm1-Tm2 0.5 0.5 ° C
The transparent polyolefin resin cup of the present embodiment is excellent in transparency by satisfying the above characteristics, and is characterized in that the haze of the molded article is particularly low, and the impact resistance at low temperature is high. Is a feature. These features are contradictory and there was no resin to fill at the same time.

  The transparent polyolefin resin cup of the present embodiment is achieved by, for example, drawing at a temperature 2 to 10 ° C. lower than the melting point after adding a crystal nucleating agent or layered silicate at 300 ppm or more in order to have the above characteristics. Be done. And the transparent polyolefin resin cup of this Embodiment exhibits the characteristic of the area | region of the transparency which can not reach to the bottom by mixing only a filler, a crystal nucleating agent, etc. at all.

  In the present embodiment, for example, the above characteristics are satisfied by forming a flat plate, a sheet, or a molded article once by press molding, sheet extrusion molding, or the like and then stretching at a temperature lower by 2 to 10 ° C. than the melting point of the resin. A transparent polyolefin resin cup can be obtained.

  Conventionally, a molded article such as a sheet is reheated to the melting point or higher and melted, and then extrusion molding or vacuum molding is performed. In this case, when the molded article is cooled and solidified, the polyethylene is whitened by crystallization and becomes opaque. Can not get the haze. In the case of cup molding, the sheet is pushed by a stick (plug) or a mold and formed by extrusion molding or vacuum molding or both, but in the case of a crystalline resin, it must be heated to a melting point or more and in the case of a noncrystalline resin. It is natural for the parties to perform molding after heating to a temperature higher than the softening point. For example, the transparent polyolefin resin cup of the present embodiment cups a molded article such as a sheet by tensile stretching at a melting point or less. Such a technology, which is achieved only after shaping, is a technology that can not be conceived at all in the extension of the prior art, which is completely different from the conventional wisdom.

  When melted, the resin has almost no strength at melting when compared to the tensile strength at normal temperature, but even at a melting point of 5 to 20 ° C., the strength is relatively low and tension can be performed relatively easily.

  The reason for becoming transparent when stretched in the range of 5 to 20 ° C below the melting point is considered that the spherulites in the resin are aligned in the stretching direction by stretching, and in the case of polyethylene, the lamellas in the spherulites are loosened and aligned in the stretching direction Be It is also considered that the lamination direction of lamellas is inclined in a certain direction without reaching the alignment. Since the resin chain of the amorphous part is also extended in the same way as the resin chain of the spherulite is extended, the refractive index of the crystalline part and the amorphous part is nearly equal, and therefore it is considered that the transparency is expressed. Be

  However, even with this method, the transparency may be poor due to the scattering of light transmitted through the container. This is considered to be light scattering because the rearranged lamella still has irregular parts. On the other hand, it is considered that the lamella of polyethylene before stretching is large, and it can be reduced until it can not be finely stretched until the influence of light can not be reached by tensile stretching.

  Nucleating agents, kaolin and talc, when added in large amounts, are believed to lower transparency by themselves, but to promote micronization and rearrangement of lamellae.

  While many polypropylene nucleating agents are known, polyethylene nucleating agents are hardly known hitherto, and cyclohexane-1,2-dicarboxylic acid salts can be exemplified as effective examples.

  The transparency of the cup is achieved, for example, by setting the tensile speed at molding to 50 mm / min or more and the draw ratio to 4 or more.

  On the other hand, when forming a cup shape from a sheet, the portion near the mouth of the cup may remain undrawn and white. This is due to the necking phenomenon observed in the tensile test of polyethylene when drawing polyethylene, and since the fracture strength of the spherulites is much stronger than the strength at which the lamellae of the polyethylene are unraveled, the ball is firstly pulled by tensile drawing. It is thought that this is because the destruction of the next spherulite does not occur until the crystal is broken and the lamella of the broken part is extended.

The resin used in the present embodiment is not particularly limited. For example, although it is an opaque crystalline resin, it exhibits transparency when it is drawn at a temperature 5 to 20 ° C. lower than the melting point and shaped as a cup, What is necessary is just the thing with high low temperature impact resistance as a cup. The resin exhibiting transparency by stretching is not particularly limited, and examples thereof include polyolefins such as polyethylene, polypropylene and polybutene and copolymers thereof with α-olefins, vinyl acetate and the like, addition systems of rubber components, polystyrene and rubber components Examples thereof include high impact polystyrenes contained, polyester resins obtained by imparting crystallinity to PET, PEN, and a part of comonomers as rigid cyclohexane dialcohols, polycarbonate resins, polyvinyl chloride and polyvinylidene resins, and the like. Among them, crystalline resins are often opaque or colored due to their molecular structure in general molding, and are not particularly limited as resins that can achieve colorless and transparent, but, for example, polyolefins such as polyethylene, polypropylene and polybutene and α-olefins with them It can be mentioned. A high density polyethylene resin is preferred from the viewpoint of low temperature impact resistance and rigidity at -30 ° C as a cup.
As a thing which improves the transparency of a cup, a nucleating agent, kaolin, a talc etc. are mentioned. As a crystal nucleating agent, the crystal nucleating agent shown to following General formula (1) is mentioned, for example. The transparent polyolefin resin cup of the present embodiment preferably contains 300 to 2000 ppm (based on mass) of the crystal nucleating agent.

In the above formula (1), M ₁ and M ₂ are selected independently from each other from the group consisting of calcium, strontium, lithium, zinc, magnesium and monobasic aluminum, and further R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ and R ₁₀ are independently selected from each other from the group consisting of hydrogen and C ₁ -C ₉ alkyl, and further located adjacent to each other Any two R _{3 to} R ₁₀ alkyl groups may optionally be linked to form a carbocyclic ring.

An example is a compound of the following general formula (2) in which R _{1 to} R ₁₀ are hydrogen, and it can be obtained from Milliken Japan Co., Ltd. under the product name EXP-20.

  In the transparent polyolefin resin cup of the present embodiment, the content of each of the crystal nucleating agents is preferably 300 ppm to 2000 ppm, more preferably 500 ppm to 1500 ppm, and still more preferably 700 ppm to 1000 ppm, based on mass. . When the content of the crystal nucleating agent is 300 ppm or more, the crystallization rate is sufficiently fast, and when it is 2000 ppm or less, the effect of improving the transparency and eliminating the whitening portion corresponding to the content is observed.

  It is preferable that the transparent polyolefin resin cup of the present embodiment contains 0.1% by mass or more and 20% by mass or less of the layered silicate. The “layered silicate” used in the present embodiment refers to a silicate in which a sheet in which metal ions and silicic acid are connected is formed in a layered manner. The layered silicate is not particularly limited, but specifically, for example, kaolin, lizardite, amesite, keriaite, Burcherin, Grinalite, Nepoite, Brindriite, Freiponite, audite, Kronstedite, percolite , Kaolinite, dickite, nacrite, halloysite, antigolite, chrysotile, talc, willemite, pyrophyllite, saponite, hectorite, sauconite, souvtenite, Steen hordeite, montmorillonite, beidellite, nontrolite, volkon scoreite And vermiculite, biotite, phlogopite, iron mica, yeastite, phlogopite, polylithionite, muscovite, sericite, ceradonite, mica of abrasive part, soda mica and the like. Layered silicates often contain water between their layers, but those which have been subjected to a calcination treatment are preferred. Among these, the layered silicate preferably contains kaolin or talc.

  Further, the layered silicate is preferably one obtained by crushing after firing, and more preferably one having an average particle diameter of not less than 0.2 μm and not more than 5.0 μm, more preferably not less than 0.5 μm and not more than 2.0 μm. Some are more preferable, and those which are 1.0 μm or more and 2.0 μm or less are more preferable. By the average particle diameter being 0.2 μm or more, the transparency of the cup tends to be more excellent, and by being 5.0 μm or less, the inhibition of the transparency of the cup by particles of the silicate itself is also reduced There is a tendency. A more preferable form is one obtained by firing and grinding hydrous kaolin. The average particle size can be measured using a laser diffraction scattering method.

  The content of the layered silicate in the transparent polyolefin resin cup of the present embodiment is preferably 0.1% by mass to 20% by mass, and more preferably 0.5% by mass to 10% by mass. It is more preferably 1% by mass or more and 5% by mass or less. When the content of the layered silicate is 0.1% by mass or more, the effect of improving the transparency of the cup tends to appear more, and when the content is 20% by mass or less, it is attributed to the particles of the layered silicate itself It also tends to be able to suppress the decrease in the transparency of the cup.

  In the transparent polyolefin resin cup of the present embodiment, the content of kaolin is preferably 300 ppm to 20000 ppm, more preferably 500 ppm to 10000 ppm, and still more preferably 1000 ppm to 5000 ppm, based on mass. If the content of kaolin is within the above range, the cup is transparent and the coloration effect of the color of kaolin itself is not seen.

In the transparent polyolefin resin cup of the present embodiment, the content of talc is preferably 300 ppm to 10000 ppm, more preferably 500 ppm to 5000 ppm, and still more preferably 700 ppm to 3000 ppm, based on mass. If the content of talc is in the above range, the cup tends to be transparent.
In the case of a beverage cup, when the visibility of the contents is required, the cup side is required to have high transparency. The upper surface of the cup is sealed with a film or the like, and the bottom surface is hidden when it is erected, so the side surface needs to be transparent.

  The transparency as a cup is indicated by the haze. The transparent polyolefin resin cup of the present embodiment has a haze of 15% or less, preferably 10% or less, more preferably 8% or less, and particularly preferably 5% or less. The lower limit of the haze on the side surface of the cup is not particularly limited, and is, for example, 2%.

  It is known that the value of haze depends on the thickness, and the thicker the thickness is, the worse (the higher) the haze is. On the other hand, even if the material is not very low in haze, the haze is reduced by thinning, and therefore the influence of thickness on transparency is large. When the thickness is 0.1 mm or less such as film, transparency can be obtained by highly stretching or super-stretching in the case of fibers, but if it is applied to a thickness of 0.1 mm or more, whitening or tearing occurs and a transparent container I can not get The iced coffee cup is required to be self-supporting and rigid in addition to impact resistance, and therefore needs a thickness, and a material having a low haze is required even if the thickness is large.

  On the other hand, when the thickness is large, the rigidity and the strength increase but the amount of resin used increases and the thickness increases so that the haze becomes worse (higher). On the other hand, if the thickness is thin, it will not stand alone, and if it is held by hand it may be deformed or crushed. Therefore, the thickness of the side surface of the transparent polyolefin resin cup of the present embodiment is 100 μm or more, preferably 100 μm to 5 mm, more preferably 200 μm to 3 mm, and still more preferably 300 μm to 1 mm.

  The thickness of the cup is preferably in the range of the entire cup, but it may be partially transparent like a window within the range of thickness.

  By setting the thickness to 100 μm or more, the cup becomes self-supporting and becomes rigid without any trouble in handling. Further, by setting the thickness to 5 mm or less, the cup can achieve transparency at an appropriate draw ratio. In addition, even if thickness is 5 mm or more, a haze can be 15% or less, if an appropriate draw ratio can be achieved.

  The haze is correlated with the thickness, and the thinner the thickness, the lower the haze and the thicker the thickness, the higher the haze. As the thickness increases, the degree of reduction of the haze with respect to the thickness increase decreases, and when it exceeds 3 mm, the value of the haze hardly changes.

  The relationship of the haze with respect to the thickness of the press board of polyethylene is shown in FIG. The smaller the thickness is, the lower the haze is, and when the thickness is 1 mm or more, the degree of the deterioration of the haze accompanying the increase in thickness is smaller. In the case of polyethylene, it is known that the lower the density, the lower the haze of a molded article formed after melting, such as press molding, injection molding or blow molding. However, when the haze is lowered, the rigidity is also lowered, and the resin having a haze of about 10% is very soft and the rigidity as a cup is insufficient.

When the thickness of the transparent polyolefin resin cup of the present embodiment is 1 mm or less, it is preferable that the relationship between the thickness t mm and the haze y% satisfy the following relationship.
y ≦ 33 × t
Also, the following relationship is satisfied between 1 mm and 3 mm.
y ≦ 15.7 × t + 17.3
By satisfying the above relationship, the cup has sufficient transparency. The transparency of the molded article also depends on the thickness, and even for an opaque material, the transparency appears when it is as thin as several tens of μm like a film. On the other hand, it is known that the transparency depends on the thickness, the thicker the thickness is, the worse the haze is, and the haze is proportional to the thickness up to a thickness of about 1 mm. Since the thickness varies depending on the molded product, it is necessary to use the relational expression of thickness and haze value. On the other hand, when the thickness exceeds 1 mm, the rate of change of the haze value due to the thickness change becomes small, and when it exceeds 3 mm, it does not change anymore.

Preferably, the relationship of 1 mm or less is satisfied.
y ≦ 30 × t
Also, the following relationship is satisfied between 1 mm and 3 mm.
y ≦ 15 × t + 15
More preferably, the relationship of 1 mm or less is satisfied.
y ≦ 25 × t
Also, the following relationship is satisfied between 1 mm and 3 mm.
y ≦ 12.5 × t + 12.5
When it exceeds 3 mm, the haze is 64.4% or less.

  On the other hand, when the transparent polyolefin resin cup of the present embodiment measures the melting temperature of the cup side surface by the method of measuring the melting temperature by the differential thermal analyzer (DSC) prescribed in JIS K69222, the first melting temperature Tm1 and the second melting temperature Tm2 satisfies the following relationship.

Tm1-Tm2 0.5 0.5 ° C
Sufficient transparency can be exhibited by setting the melting point difference (Tm1-Tm2) to 0.5 ° C. or higher. The higher the melting point difference (Tm1-Tm2), the better the transparency. The upper limit is not particularly limited. However, the theoretical upper limit is the melting point difference from the perfect crystalline form (100% crystallinity) of the resin.

  The melting temperatures Tm1 and Tm2 by DSC method indicate the melting point of the crystalline resin. Tm2 is called the second melting temperature, and it is the melting temperature when the sample is melted once, slowly cooled and crystallized again, and it is the melting temperature specified in JIS K6922-2 is there. On the other hand, Tm1 is a sample obtained by pulling and stretching a molded article at a temperature 2 to 10 ° C. lower than the melting point to make a sample transparent and measuring the melting temperature as it is. Since Tm1 is usually quenched with a mold at the time of shaping, the temperature is generally lower than the melting point Tm2 because the crystal is fine and the degree of crystallization is lowered, so Tm1-Tm2 takes a negative value. However, in the present application, by being stretched by drawing at a temperature 2 to 10 ° C. lower than the melting point Tm 2, the lamella which is a folded structure of polyethylene or polypropylene is stretched, and the amorphous part existing between crystals is also stretched similarly. The temperature of Tm1 is higher than the original melting point Tm2 in order to have a highly ordered structure in the stretching direction as a whole.

The relationship between Tm1 and Tm2 is preferably Tm1-Tm2> 0.7 ° C.
More preferably, Tm1-Tm2> 1.0 ° C.
It is.

  Since the transparent polyolefin resin cup of the present embodiment has a second melting point lower than the first melting point, Tm1-Tm2 takes a positive value, and the difference is 0.5 ° C. or more.

  In the transparent polyolefin resin cup of the present embodiment, the molded product is extruded by the method of ISO 1133 against the density D1 of the cup side surface measured by the method D defined in JIS K7112, and the density D2 measured by the method of JIS K7112 is It is preferable to satisfy the following relationship.

D1-D2 ≧ 0.5 kg / m ³
In the transparent polyolefin resin cup of the present embodiment, sufficient transparency can be obtained by setting the density difference (D1-D2) to 0.5 kg / m ³ or more. The upper limit is not particularly limited because the transparency increases as the density difference (D1-D2) increases, but the theoretical upper limit is the density difference with the completely crystalline form (100% crystallinity) of the resin.
The transparent polyolefin resin cup of the present embodiment more preferably satisfies the following relationship.

D1-D2 ≧ 0.7 kg / m ³
More preferably, the following relationship is satisfied:
D1-D2 ≧ 1.0 kg / m ³
The density measured by the method of JIS K7112 is sufficiently annealed and crystallized according to the method of JIS K7112, but the molded product is usually rapidly cooled, so the degree of crystallization is low and the density is also lower than the annealing density. Therefore, D1-D2 is usually a negative value. The transparent polyolefin resin cup of the present embodiment is preferably D1-D2 because it exhibits transparency when the degree of crystallinity is improved by stretching and the degree of crystallinity is improved more than the annealed degree of crystallinity. The positive value is taken, and the greater the difference, the better the transparency.

In the transparent polyolefin resin cup of the present embodiment, the transparency is improved as the density is lower, but the rigidity is lowered, so that the density measured by the method prescribed in JIS K7112 is 935 kg / h from the viewpoint of self-supportability and rigidity as a cup. it is preferably m ³ or more. Transparent polyolefin resin cup of the present embodiment, compatible transparency and rigidity by making the density of 935 kg / m ³ or more, preferably 940 kg / m ³ or more, more preferably 945 kg / m ³ or more, more preferably It is 949 kg / m ³ or more. On the other hand, the upper limit of the density is, for example, the density of a fully crystallized polyethylene, but the higher the density, the lower the transparency, so 972 kg / m ³ or less is preferable, 969 kg / m ³ or less is more preferable 964 kg / m ³ or less Is more preferably 959 kg / m ³ or less.

  The polyethylene resin used in the present embodiment exhibits various features and physical properties depending on the polymerization method and catalyst system, but is not particularly limited. Even if it is below the melting point, the behavior at the time of stretching is close to the molten state, and one with relatively high melt tension or one with the characteristics of strain hardening that tension increases at high speed tension is preferable, so-called chromium catalyst A polyethylene obtained by polymerizing using a Phillips catalyst as a catalyst, a high pressure low density polyethylene obtained by radical polymerization at high temperature and pressure, and a polyethylene resin copolymerized using α-olefin having 10 or more carbon higher olefins are preferably used. These may be used alone or in combination with other resins, other high density polyethylenes or low density polyethylenes. In the case of copolymerization of higher olefins, those polymerized with a metallocene catalyst are preferable in view of the incorporation efficiency of the higher olefin into the molecule. Thus, even if it is solid, thickness can be made more uniform at the time of tensile drawing by using a thing with a comparatively high melt tension, and a grade with the property of strain hardening. If the melt tension is too strong, a large amount of force is required at the time of drawing, and since it may not withstand elongation and may break, it is also preferable to mix other resins and adjust the viscosity.

In the transparent polyolefin resin cup of the present embodiment, it is preferable that the transparent polyolefin resin contains a high density polyethylene resin, and the density measured by the method prescribed in JIS K6922-1 is 935 kg / m ³ or more.

  The transparent polyolefin resin cup according to the present embodiment preferably has a total absorbed energy of 2 J or more in a drop impact test at -30 ° C on the side surface of the cup. The drop-ceiling impact test measures the impact resistance by dropping a missile with a weight attached to a flat plate, and the total absorbed energy is the sum of the energy for crack initiation and the energy for crack propagation. The drop strength is harder to break as the energy generating the crack is higher, and as the energy propagating through the crack is higher, the damage to the fracture becomes difficult. The total absorbed energy of the transparent polyolefin resin cup of the present embodiment is preferably 2.5 J or more, more preferably 3 J or more. The upper limit of the total absorbed energy is not particularly limited, and is, for example, 12 J.

  The transparent polyolefin resin cup of the present embodiment is high in rigidity and excellent in buckling strength as compared with a resin of the same thickness before stretching, and tends not to cause whitening due to bending. In addition, it tends to be able to obtain a uniform product around the meat. In addition, since the drawing speed can also be 1000 mm / min or more, high-speed moldability tends to be excellent.

  Furthermore, the storage stability of the contents is excellent, and whitening by contact with water at 100 ° C. or less, devitrification, and large deformation due to shrinkage tend not to occur.

  When polyolefin is used, it tends to be transparent to infrared light and ultraviolet light as well as visible light.

  The present invention will be described based on examples.

  The physical property measurement and the molding method are as follows.

(1) Melt flow rate (MFR)
The measurement was carried out at a temperature of 190 ° C. and a load of 2.16 kg according to the method of JIS K 7210-1.

(2) Density (D1, D2)
The density D1 cut out the test piece from the side of a cup, and measured the density by the density gradient tube method of the D method of JISK7112.

  The density D2 is annealed at 120 ° C. for 1 hour in a nitrogen atmosphere for 1 hour after the extruded strand is annealed at 120 ° C. under a resin temperature of 190 ° C. and a load of 2.16 kg according to the method of ISO 1133. The density was measured by the density gradient tube method of

(3) Melting point (Tm1, Tm2)
It measured by the method of JISK6922-2. After holding Tm1 at 50 ° C. for 1 minute using DSC, the temperature was raised to 180 ° C. in the case of polyethylene (PE) at a temperature rising rate of 10 ° C./min, and the peak top temperature of the exothermic curve was taken as melting point Tm1. Tm2 is further held for 5 minutes after reaching 180 ° C., cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min, held for 5 minutes, and then peaked in the exothermic curve when heated at a temperature raising rate of 10 ° C./min. The melting point Tm2 was taken as the temperature of

(4) Drop cone impact Using a drop cone impact tester manufactured by Toyo Seiki, the striker diameter is 12.5 mm, the holder diameter is 54 mm, the weight is 6.5 kg, and the drop height is 50 cm, and it is cooled to -30 ° C by a cooling device. Did. When a graph of energy against time was taken, the crack generation energy up to the peak top was taken as the crack propagation energy after the peak top, and the sum was taken as the drop impact energy.

(5) Haze A sample was taken from the side of the formed cup, the thickness of the measurement portion was measured, and the haze was measured with a haze meter.
(6) Whitening at the edge of the cup When observing the side of the formed cup, if there is a white whitening portion remaining unstretched in the portion near the edge of the top of the cup, there is "all";"None", the entire cup is opaque white and "whole".
(7) Formability When the cup was formed, it was broken when it was formed, and when it had a tear in the longitudinal direction, the formability was evaluated as x, and the one which could be formed without tears and cracks was evaluated as o.
[Catalyst preparation 1]
[Polyethylene resin composition (PE1)]
6.2 g (8.8 mmol) of triethylammonium tris (pentafluorophenyl) (4-hydroxyphenyl) borate was added to 4 L of toluene and stirred at 90 ° C. for 30 minutes. Next, 40 ml of a toluene solution of 1 mol / L trihexylaluminum was added to this solution, and the mixture was stirred at 90 ° C. for 1 minute. On the other hand, silica P-10 (manufactured by Fuji Silysia Co., Ltd .: trade name) was treated with a nitrogen stream at 500 ° C. for 3 hours, and the treated silica was placed in 1.7 l of toluene and stirred. The above triethylammonium tris (pentafluorophenyl) (4-hydroxyphenyl) borate and a toluene solution of trihexylaluminum were added to the silica slurry solution, and the mixture was stirred at 90 ° C. for 3 hours.

Next, 206 ml of a toluene solution of 1 mol / L trihexylaluminum was added, and the mixture was further stirred at 90 ° C. for 1 hour. Thereafter, the supernatant was decanted 5 times using toluene at 90 ° C. to remove excess trihexylaluminum. Dark purple titanium (N-1,1-dimethylethyl) dimethyl (1- (1,2,3,4,5-eta) -2,3,4,5-tetramethyl-, 0.218 mol / L 20 ml of a solution of 2,4-cyclopentadien-1-yl) silanaminate ((2-) N)-(( ⁴ -1,3-pentadiene) in ISOPARTME (manufactured by Exxon Chemical Company, USA) is added to the above mixture 3 The mixture was stirred for time to obtain a green supported catalyst. A portion of the obtained supported catalyst was placed in a 1.5 L reactor together with 0.8 L of dehydrated and deoxygenated hexane. The mixture gas ratio of ethylene, 1-butene, and hydrogen was adjusted by setting the temperature in the vessel to 77 ° C., and the total pressure was set to 0.8 MPa with 0.43% of 1-butene and 2600 ppm of hydrogen.

  By supplying the mixed gas of the above composition, polymerization was performed for 2 hours while maintaining the total pressure at 0.8 MPa to obtain a powder. 300 ppm of calcium stearate and EXP 20 manufactured by Milliken Japan Co., Ltd. as a crystal nucleating agent were added to a concentration of 500 ppm, and mixed by stirring with a mixer. The composition (PE1) is extruded by extruding this mixture under conditions of a cylinder temperature of 200 ° C. and an extrusion amount of 35 kg / hour using a twin screw extruder (TEX44HCT-49PW-7V manufactured by Japan Steel Works, Ltd.) with a cylinder diameter of 44 mm. Obtained.

[Polyethylene resin composition (PE2)]
Pellets (PE2) were obtained in the same manner as PE1, except that kaolin (manufactured by BASF Japan Ltd .: Satinton W (registered trademark)) was changed to 10000 ppm in place of the crystal nucleating agent EXP20.

[Polyethylene resin composition (PE3)]
Pellets (PE3) were obtained in the same manner as PE1, except that the nucleating agent EXP20 was not added.
[Catalyst preparation 3]
(1) Synthesis of chromium oxide catalyst (I) 4 mol of chromium trioxide is dissolved in 80 liters of distilled water, and 20 kg of silica (grade 952 made by W. R Grace and Company) is immersed in this solution, 1 at room temperature After stirring for a period of time, the slurry is heated to distill off water, and then dried under reduced pressure at 120 ° C. for 10 hours, and then dried by flowing dry air at 600 ° C. for 5 hours to calcine chromium. A chromium oxide catalyst (I) containing 0% by weight was obtained.

(2) Synthesis of organoaluminum compound (II) 100 moles of triethylaluminum, 50 moles of methylhydropolysiloxane (viscosity at 30 ° C .: 30 centistokes) (based on Si), 150 liters of n-hexane in a pressure-resistant container under a nitrogen atmosphere The reaction solution was taken out and reacted at 50 ° C. under stirring for 24 hours to prepare an Al (C ₂ H ₅ ) _2.5 (OSi · H · CH ₃ · C ₂ H ₅ ) _0.5 hexane solution. Next, 100 moles (based on Al) of this solution is transferred to a 600 liter reactor under a nitrogen atmosphere, and a mixed solution of 50 liters of ethanol and 50 liters of n-hexane is added with stirring at -10 ° C, and 50 ° C after addition. The temperature was raised to a temperature, and reaction was carried out at this temperature for 1 hour to prepare an Al (C ₂ H ₅ ) _2.0 (OC ₂ H ₅ ) _0.5 (OSi · H · CH ₃ · C ₂ H ₅ ) _0.5 hexane solution.

(3) Synthesis of titanium catalyst (III) 3 liters of trichlorosilane as a 2 mol / liter n-heptane solution was charged into a sufficiently nitrogen-substituted 15 liter reactor, and kept at 65 ° C. with stirring to give a compositional formula AlMg ₆ (C ₂ H ₅ ) ₃ (nC ₄ H ₉ ) _6.4 (On-C ₄ H ₉ ) _5.6 1 liter of an n-heptane solution (5 moles in terms of magnesium) of the organic magnesium component shown in _5.6 The reaction mixture was further reacted under stirring at 65 ° C. for 1 hour. After completion of the reaction, the supernatant was removed and washed with 7 liters of n-hexane four times to obtain a solid material slurry. The solid was separated, dried and analyzed. As a result, it contained 7.45 millimoles of Mg per gram of solid.

  Among the above, a slurry containing 500 g of solid was reacted at 50 ° C. for 1 hour with stirring, with 0.93 liter of n-hexane solution of 1 mole / liter of n-butyl alcohol. After completion of the reaction, the supernatant was removed and washed once with 7 liters of n-hexane. The slurry was kept at 50 ° C., and 1.3 l of n-hexane solution of 1 mol / l of diethylaluminum chloride was added under stirring and reacted for 1 hour. After completion of the reaction, the supernatant was removed and washed twice with 7 liters of n-hexane. The slurry was kept at 50 ° C., 0.2 liter of n-hexane solution of 1 mole / liter of diethylaluminum chloride and 0.2 liter of n-hexane solution of 1 mole / liter of titanium tetrachloride were added and reacted for 2 hours. After completion of the reaction, the supernatant was removed, the solid catalyst was isolated and washed with hexane until free halogen was not detected. The solid catalyst had 2.3 wt% titanium.

(4) Production of Polyethylene Resin A In a single-stage polymerization process, polymerization was performed in a 230 L volume polymerization vessel. The polymerization temperature is 84 ° C., and the polymerization pressure is 0.98 MPa. To 50 g of the chromium oxide catalyst (I) synthesized in (1), 0.03 mol (based on Al) of the organoaluminum compound (II) prepared in (2) is added to this polymerization vessel and allowed to react at room temperature for 1 hour The organic aluminum compound obtained by reacting the obtained solid catalyst with ethanol and triethylaluminum at a molar ratio of 0.98: 1 at a rate of 2 g / hr has a concentration of 0.08 mmol / l in a polymerization vessel. The supply was adjusted to be Purified hexane is fed at a rate of 60 L / hr, ethylene is fed at a rate of 12 kg / hr, hydrogen as a molecular weight regulator is fed so that the gas phase concentration becomes about 5 mol%, and polymerization is carried out. A polyethylene resin A having a density of 963 kg / m ³ was produced at 0 g / 10 min.

(5) Production of polyethylene resin B First, in order to produce low molecular weight components in the first stage polymerization, using a stainless-steel polymerizer 1 having a reaction volume of 300 liters, the conditions of a polymerization temperature of 83 ° C. and a polymerization pressure of 1 MPa The catalyst was introduced at a rate of 1.4 mmol (based on Ti atoms) / hr, 20 mmol (based on metal atoms) / hr of triisobutylaluminum, and 40 liters / hr of hexane as the above solid catalyst (III). Hydrogen was used as a molecular weight modifier, and polymerization was carried out by supplying a hydrogen concentration of 70 mol% with respect to ethylene. The polymer slurry solution in the polymerizer 1 was introduced into a flash drum with a pressure of 0.1 MPa and a temperature of 75 ° C., and unreacted ethylene and hydrogen were separated and then introduced into the polymer volume 2 with a reaction volume of 250 liters by pressurizing with a slurry pump . In the polymerization vessel 2, under conditions of a temperature of 77 ° C. and a pressure of 0.5 MPa, triisobutylaluminum was introduced at a rate of 7.5 mmol / hr and hexane at a rate of 40 l / hr. To this, ethylene, hydrogen and butene-1 are introduced so that the gas phase concentration of hydrogen is about 9 mol% and the gas concentration of butene is about 10 mol%, The high molecular weight portion is polymerized so that the weight ratio of the high molecular weight portion generated by the polymerization vessel 2 to the amount is 1.0, and a polyethylene having an MI of 0.43 g / 10 min and a density of 940 kg / m ³ Resin B was produced. The MI of the low molecular weight portion produced by the polymerization vessel 1 was 70 g / 10 min, and the density was 972 kg / m ³ .

(6) Production of polyethylene resin composition (PE4) The powders of polyethylene resins A and B produced as described above were mixed in a weight ratio of 39 to 61, and then 300 ppm of calcium stearate and Adeka were added to this mixture. Add 300 mg of Adekastab (registered trademark) AO-50, 500 ppm of Adekastab (registered trademark) 2112, and EXP20 manufactured by Milliken Japan Co., Ltd. as a crystal nucleating agent to a concentration of 500 ppm, and stir and mix in a mixer. The composition (PE 4) was extruded by extruding this mixture under conditions of a cylinder temperature of 200 ° C. and an extrusion amount of 35 kg / hour using a twin screw extruder (TEX44HCT-49PW-7V manufactured by Japan Steel Works, Ltd.) having a cylinder diameter of 44 mm. Obtained.

Production of polyethylene resin composition (PE5) Pellets (PE5) were obtained in the same manner as PE4, except that kaolin (manufactured by BASF Japan Ltd .: Satinton W (registered trademark)) was changed to 10000 ppm instead of the crystal nucleating agent EXP20. .

Production of Polyethylene Resin Composition (PE6) Pellets (PE6) were obtained in the same manner as PE4, except that the nucleating agent EXP20 was not added.
Create Sheet
It shape | molded by the method of JISK7151 by compression molding. The pellets were heated and melted at a resin temperature of 200 ° C. to form a 300 mm square sheet having a thickness of 1.2 mm. The cooling was quenched using a cooling press according to cooling method C. Prior to molding, a blend system of a plurality of resins was pelletized by a 20 mm extruder and used for molding.
[Cup molding]
The sheet was clamped and heated between the heaters so that the temperature of the sheet was 5 to 10 ° C. lower than the melting point (Tm 2) of the resin, and pressed from above with the cup-shaped cavity positioned below The cup was then shaped by blowing in air. The molding temperature and the extrusion rate are shown in Table 1.
Example 1
A polyethylene resin (PE1) was used as the polyethylene resin. A sheet was prepared, and a cup was formed at a sheet temperature of 120 ° C. and a push bar speed of 10 mm / min to measure physical properties and the like. The measurement results of physical properties and the like are shown in Table 1.
Example 2
Molding was performed in the same manner as in Example 1 except that the polyethylene resin was changed to PE2, and physical properties and the like were measured. The measurement results of physical properties and the like are shown in Table 1.
Comparative Example 1
Molding was performed in the same manner as in Example 1 except that the polyethylene resin was changed to PE3, and physical properties and the like were measured. The measurement results of physical properties and the like are shown in Table 1.
[Reference Example 1]
A sheet of polyethylene resin (PE3) was prepared and its density and melting point were measured. The measurement results are shown in Table 1.
[Example 3]
A cup was molded in the same manner as in Example 1 except that the polyethylene resin was replaced by the polyethylene composition (PE4). The measurement results of physical properties and the like are shown in Table 1.
Example 4
A cup was molded in the same manner as in Example 1 except that the polyethylene resin was replaced with the polyethylene composition (PE5). The measurement results of physical properties and the like are shown in Table 1.
Comparative Example 2
It shape | molded similarly to Example 1 except having replaced polyethylene resin with the polyethylene composition (PE6), and measured the physical property. The measurement results of physical properties and the like are shown in Table 1.
[Reference Example 2]
The density and melting point of the sheet of the polyethylene composition (PE6) were measured. The measurement results are shown in Table 1.

Claims (6)

Transparent polyolefin resin cup meeting the following characteristics.
(1) A crystal nucleating agent or layered silicate containing 300 ppm or more (2) The thickness of the cup is 100 μm or more and the haze on the side of the cup is 15% or less (3) Melting temperature specified in JIS K6922-2 When the melting temperature of the cup side is measured by the method of measurement, the first melting temperature Tm1 and the second melting temperature Tm2 satisfy the following relationship: Tm1-Tm2 ≧ 0.5 ° C. The transparent polyolefin resin cup according to claim 1, wherein the transparent polyolefin resin contains a high density polyethylene resin, and the density measured by the method prescribed in JIS K7112 is 935 kg / m ³ or more. The molded article is extruded according to the method of ISO1133 and the density D2 measured according to the method of JIS K7112 satisfies the following relationship with respect to the density D1 of the cup side surface measured by the method D defined in JIS K7112: Polyolefin resin cup.
D1-D2 ≧ 0.5 kg / m ³   The transparent polyolefin resin cup according to claim 2 or 3, wherein the transparent polyolefin resin comprises a polyethylene resin polymerized by a chromium catalyst.   The transparent polyolefin resin cup according to claim 2 or 3, wherein the transparent polyolefin resin comprises a low density polyethylene resin polymerized by a high pressure method.   The transparent polyolefin resin cup according to any one of claims 1 to 5, wherein the total absorbed energy in a drop impact test at -30 ° C for the side surface of the cup is 2 J or more.