JP4778283B2 - Resin composition and laminate - Google Patents

Description

  The present invention relates to a resin composition suitable as a heat seal material and a laminate having a heat seal layer of the composition. More specifically, the present invention has adhesiveness to an aluminum foil substrate and the like, and has polystyrene foam or resistance. Easily openable lid that shows moderate heat-sealing properties for various containers such as impact polystyrene containers, and exhibits a smooth and light peeling resistance when peeling the lid from the container, and remarkably excellent peel feeling The present invention relates to a laminate useful as a material for producing a resin composition suitable as a heat seal material such as a material and an easily openable lid having the composition heat seal layer.

In recent years, foods and drinks such as cup noodles, jelly, yogurt, tofu, etc. have been obtained by laminating a sealing agent layer on an aluminum foil on a container body made of expanded polystyrene such as so-called polystyrene paper (PSP) or impact-resistant polystyrene (HIPS). What was stored in the airtight container which heat-sealed the easy-opening lid | cover consisting of a laminated body is marketed widely.
For example, as a lid for cup noodles, a laminate in which a printing paper layer is formed on the outer side of an aluminum foil container via a polyethylene protective film, and a heat seal layer is formed on the container body side of the aluminum foil via a polyethylene layer. The thing of a structure can be illustrated and the expanded polystyrene is used abundantly for the container main body.
The heat seal material of these containers is required to protect the contents, openability during use, good appearance of the opened portion after opening, etc. Therefore, selection of the seal material is regarded as a very important issue. Various types have been proposed and put to practical use.

  For example, Patent Document 1 discloses an ethylene / unsaturated carboxylic acid / (meth) acrylic ester copolymer or an ethylene / (meth) acrylic acid copolymer and / or an ethylene / (meta) having a melting point of less than 95 ° C. ) Mixed component with acrylic ester copolymer, low density polyethylene and / or ethylene / unsaturated ester copolymer with a melting point of 95 ° C. or higher, low crystalline ethylene / α-olefin copolymer, tackifying resin, styrene / A resin composition comprising an unsaturated carboxylic acid copolymer containing 5 to 25 mass of the tackifying resin is disclosed.

  Patent Document 2 discloses that as the component (A), ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer or ethylene / (meth) acrylic acid copolymer and / or ethylene / (meta ) 50-80 parts by mass of mixed component with acrylic ester copolymer, 5-30 parts by mass of low density polyethylene as component (B), 5-20 parts by mass of low crystalline ethylene / α-olefin copolymer as component (C) And a component derived from (meth) acrylic acid in component (A) in the resin composition (1) or more and less than 5 parts by weight as a component (D) A resin composition having a specific content of units derived from a (meth) acrylic acid ester is disclosed.

These resin compositions have excellent adhesiveness even if they are directly extrusion coated on an aluminum foil or the like used as a lid base material, and are also suitable for expanded polystyrene that is frequently used as a container body constituent material. It has excellent strength at the time of seal peeling, and the peeling sound generated at the time of peeling is not so loud. Furthermore, it has excellent heat resistance oil resistance and the like, and exhibits excellent heat sealing performance.
Further, the processing speed can be considerably increased, which is excellent in terms of productivity.

However, although the heat sealing material made of the resin composition of Patent Documents 1 and 2 described above does not have a very high peeling sound at the time of peeling, it is difficult to say that the peeling feel is sufficiently good.
That is, each of the resin compositions is blended with a predetermined amount of low density polyethylene for the purpose of maintaining heat resistance and a low crystalline ethylene / α-olefin copolymer for the purpose of improving slipperiness and workability.
Because of this, the easy-open lid of the heat seal layer is not zipped when peeled, that is, not a smooth and light resistance to the force applied at the time of peeling. For example, when opening and closing a fastener As such, it exhibits a tingling or crispy resistance feeling based on intermittent movement.

  In particular, recently, depending on the application, the tendency to demand good feeling at the time of peeling, that is, good feeling of peeling rather than sealing strength characteristics such as peeling strength and durability strength of the sealing material has been increasing.

JP 2001-198110 A JP 2005-187744 A

  As a result of intensive investigations to develop a resin composition for a sealing material that can sufficiently meet the above-mentioned recent demands, the present inventors have determined that both low-density polyethylene and low-crystalline ethylene / α-olefin are co-polymerized from the resin composition. Excludes polymers and blends ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymers with specific ethylene / (meth) acrylic acid ester copolymers in a relatively narrow specific range and is adhesive. By not adding an imparting agent or keeping the blending amount to an extremely small amount, the feel at the time of peeling is remarkably improved without significantly deteriorating the peel strength characteristics, heat resistance, slipperiness, workability, etc. of the composition. Based on this finding, the present inventors have completed the present invention.

Therefore, the object of the present invention is to improve the feel at the time of peeling as a sealant without deteriorating various properties such as sealing strength, heat resistance oil resistance, slipperiness and workability in the above conventional resin composition for heat sealing materials. There is.
Another object of the present invention is to provide a laminate comprising a heat seal layer made of the resin composition of the present invention and suitable as a material for producing an easy-open lid or the like.

According to the present invention, (A) ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer component or ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer and ethylene / (meta ) Acrylic acid copolymer mixed component, 90-20 parts by mass, (B) ethylene / (meth) acrylic acid ester copolymer component, 10-80 parts by mass, and (C) tackifier resin component 0-20 The resin component consists of parts by mass (however, the total amount of the components (A), (B) and (C) is 100 parts by mass) , and the ethylene / (meth) acrylate copolymer (B) Flow rate (JIS
K7210-1999) is 0.1 to 500 g / 10 min, and a (meth) acrylic acid ester unit content is 5 to 30% by mass. A resin composition is provided.

In the present invention, the ethylene / (meth) acrylate copolymer (B) has a melt flow rate of 0.5 to 150 g / 10 min and a (meth) acrylate unit content of 5 What is -25 mass% is more preferable.
Further, as the ethylene / (meth) acrylic acid ester copolymer (B), the melting point of the copolymer by differential scanning calorimetry (DSC) (T: conforming to JIS K7121) and its (meth) acrylic acid ester unit It is particularly preferable to use a material whose content (X: mol%) has a relationship represented by the following formula (1).
−3.0X + 125 ≧ T ≧ −3.0X + 109 (1)

  When (A) is a mixture of ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer and ethylene / (meth) acrylic acid copolymer, ethylene / (meth) acrylic acid by mass・ (Meth) acrylic acid ester copolymer / ethylene / (meth) acrylic acid copolymer 100/0 to 60/40 are preferred.

  More preferably, the composition of the present invention contains at least one of a slip agent and an anti-blocking agent.

  According to the present invention, a heat seal material comprising the above resin composition, a laminate in which the above heat seal material is directly formed on an aluminum foil, and a lid using the above heat seal material for a heat seal layer The invention of the expanded polystyrene container or impact-resistant polystyrene container which uses the said heat seal material for a material and a heat seal layer is provided, respectively.

  The resin composition of the present invention has the above-mentioned specific configuration, as a heat seal material for a foamed polystyrene or impact-resistant polystyrene container, etc., heat sealability for a container body constituent material, adhesion to a lid substrate such as an aluminum foil, food, etc. The properties required for this type of heat seal material, such as protection of container contents, opening strength during use, heat resistance oil resistance, etc., are not significantly impaired compared to conventional heat seal materials. This is a remarkably improved peel feeling compared to conventional products, with an easy-open container lid with a heat seal layer directly extruded onto an aluminum substrate using the resin composition of the present invention, foamed polystyrene and impact resistance. A container composed of a polystyrene container body exhibits a remarkably smooth and light resistance to the force applied to the peeling when the container is opened compared to a conventional container.

  Hereinafter, embodiments of the present invention will be described in detail and specifically.

  The resin composition of the present invention comprises (A) an ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer component or a mixed component of the copolymer and an ethylene / (meth) acrylic acid copolymer. (B) An ethylene / (meth) acrylate copolymer component having a melt flow rate (MFR) and (meth) acrylate unit content in a specific range, respectively, is an essential constituent resin component, and an optional resin component It consists of a certain (C) tackifying resin component.

  In the ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer used as the component (A) of the present invention, (meth) acrylic acid is acrylic acid and / or methacrylic acid, ) Acrylic ester means acrylic ester and / or methacrylic ester, respectively.

  Specific examples of the (meth) acrylic acid ester unit in the copolymer include methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, isooctyl acrylate, acrylic acid- Examples include units composed of 2-ethylhexyl, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, and the like.

  The ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer used in the present invention has a melt flow rate (MFR) (JIS K7210-1999) of 1 to 150 g / 10 min, more preferably 1 to 100 g. / 10 minutes, and the (meth) acrylic acid unit content is preferably 5 to 15% by mass, more preferably 7 to 12% by mass, and the (meth) acrylic acid ester unit content is 5 to 25%. A mass%, more preferably 5 to 20 mass% is suitably used.

  When a mixed component is used as the component (A) of the present invention, the mixed ethylene / (meth) acrylic acid copolymer has a melt flow rate (MFR) of 1 to 500 g / 10 min, more preferably 1 to It is preferable to use one having a weight of 100 g / 10 minutes, and a (meth) acrylic acid unit content of 3 to 15% by mass, more preferably 7 to 12% by mass is suitably used.

  When using a mixed component, the blending mass ratio of the ethylene / (meth) acrylic acid copolymer to the ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer is preferably 100/0 to 60/40. Is preferably 90/10 to 70/30.

  The (B) ethylene / (meth) acrylic acid ester copolymer used as an essential resin component in the present invention has a melt flow rate (MFR: JIS K7210-1999) of 0.1 to 500 g / 10 min, more preferably 0.8. It is 5 to 150 g / 10 min, and the (meth) acrylic acid ester unit content is 5 to 30% by mass, more preferably 5 to 25% by mass.

If the melt flow rate (MFR) is outside the above range, the viscoelasticity of the resin composition obtained by blending it will be inferior, so it will not be a suitable heat seal material and will also be workable. Inferior.
Also, when the (meth) acrylic acid ester unit content is less than 5% by mass, the sealing property against the container body constituting material such as expanded polystyrene and the feel at the time of peeling are not sufficient, while those exceeding 30% by mass are suitable for laminating. Inferior to heat and oil resistance.

In the (B) ethylene / (meth) acrylic acid ester copolymer used in the present invention, a copolymer having a melting point (T) determined by differential scanning calorimetry (DSC) of the copolymer is particularly preferred as a copolymer of a preferred embodiment. : Based on JIS K7121) and the content of the (meth) acrylic acid ester unit (X: mol%) can be cited as having a relationship represented by the following formula (1).
−3.0X + 125 ≧ T ≧ −3.0X + 109 (1)
However, in the present invention, 1.7 ≦ X ≦ 12.2.

  A copolymer having a melting point and ester unit content as described above has a smaller random arrangement of ethylene units and (meth) acrylic acid ester units than a normal copolymer having good randomness, The alignment heterogeneity is high, and the polymer structure and physical properties are somewhat similar to those of block copolymers.

  Such a copolymer can be produced, for example, by performing multistage polymerization in an autoclave or polymerizing in a tubular reactor (tubular reactor) in a high-pressure radical polymerization method (for example, patents). No. 3423308, JP-A-62-273214, etc.).

In the present invention, in addition to the essential resin components (A) and (B), (C) a tackifier resin component can be blended.
Examples of the tackifying resin include aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, aromatic hydrocarbon resins, polyterpene resins, rosins, styrene resins, coumarone-indene resins, and the like.

  Examples of the aliphatic hydrocarbon resin include polymers mainly composed of mono- or diolefins having 4 to 5 carbon atoms, such as butene-1, isobutylene, butadiene, 1,3-pentadiene, and isoprene. It is done.

  Examples of the alicyclic hydrocarbon resins include resins obtained by polymerizing a diene component in the spent C4 to C5 components after cyclization and dimerization, resins obtained by polymerizing a cyclic monomer such as cyclopentadiene, and aromatic carbonization. Examples include a resin obtained by hydrogenating a hydrogen resin.

  Examples of the aromatic hydrocarbon resin include a resin mainly composed of a vinyl aromatic hydrocarbon having 8 to 10 carbon atoms such as vinyl toluene, indene, and α-methylstyrene.

  Examples of polyterpene resins include α-pinene polymers, β-pinene polymers, dipentene polymers, terpene / phenol copolymers, α-pinene / phenol copolymers, and the like.

  Examples of rosins include rosins such as gum rosin, wood rosin and tall oil, and modified products thereof. Examples of the modified products include those subjected to modification means such as hydrogenation, disproportionation, dimerization, and esterification.

The styrene hydrocarbon resin is a polymer such as styrene, vinyltoluene, α-methylstyrene, isopropenyltoluene and the like.
Among these, in the present invention, from the viewpoints of odorlessness, food hygiene, compatibility with other components, etc., a resin obtained by hydrogenating an aromatic hydrocarbon resin is most preferable.

  The resin composition of the present invention comprises (A) an ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer component, or a mixture of the copolymer and an ethylene / (meth) acrylic acid copolymer. Components, 90 to 20 parts by weight, more preferably 80 to 30 parts by weight, particularly preferably 70 to 40 parts by weight, and (B) melt flow rate (MFR) and (meth) acrylic acid ester unit content are in specific ranges, respectively. Ethylene / (meth) acrylic acid ester copolymer component, 10 to 80 parts by mass, more preferably 20 to 70 parts by mass, particularly preferably 30 to 60 parts by mass as an essential constituent resin component, and this is an optional resin component (C) The tackifier resin component is composed of 0 to 20 parts by mass, more preferably 1 to 10 parts by mass, and particularly preferably 1 to 5 parts by mass (provided that (A), (B), (C) total of components) Amount 00 is a parts by mass).

When the blending ratio of the component (A) is less than 30% by mass, it is not preferable because the obtained resin composition has poor adhesion strength to an aluminum foil and heat seal strength to a foamed polystyrene container.
Moreover, when it exceeds 80 mass%, the heat-resistant oil resistance and peeling feeling of a composition will deteriorate.

  In the resin composition of the present invention, the (C) tackifier resin component does not necessarily need to be blended, but the (C) component is (A) and (B) a total of 100 parts by mass of the resin component, By blending a small amount (for example, 1 to 5 mass) part, the low temperature sealing property and the aluminum adhesiveness are further improved.

In addition to the components (A), (B), and (C), the resin composition of the present invention requires additives such as slip agents and anti-blocking agents and other components in order to further improve the processability. It can be blended according to.
Such additives include saturated or unsaturated fatty acid amides such as stearic acid amide, oleic acid amide, erucic acid amide, palmitic acid amide, behenic acid amide, oleyl palmitamide, stearyl erucamide, N, N One or more of hydrogenated castor oil, silica, etc., such as' -methylenebisstearylamide, N, N'-ethylenebiserucamide, etc. can be used.
The amount of these used is, for example, in the range of 0.1 to 5 parts by mass, particularly 0.3 to 3 parts by mass per 100 parts by mass of the total amount of the components (A) and (B).

  In the resin composition of the present invention as described above, the MFR is preferably adjusted to 1 to 150 g / 10 minutes, particularly 5 to 50 g / 10 minutes in consideration of extrusion processability.

The resin composition of the present invention is useful as a heat seal material.
In particular, since the aluminum foil layer can be directly extrusion coated, it is useful as a sealing material for a laminated material including the aluminum foil layer.
Such extrusion coating can be performed using a single layer molding apparatus, but low density polyethylene and the above resin composition are extrusion coated on both sides of an aluminum foil using a tandem molding apparatus to reduce the printing paper. If it adheres to the density polyethylene side, the laminated lid body of 4 layer structure can also be manufactured in one process.

  Such a laminated lid material can be used as a lid material for various plastic containers for food, medicine, medical supplies, etc., and in particular, since it has an appropriate sealing strength against expanded polystyrene such as polystyrene paper (PSP), Suitable for lid materials for expanded polystyrene containers for cup noodles and heat seal layers for expanded polystyrene (PSP) containers or impact-resistant polystyrene (HIPS) containers.

Specifically, the resin composition of the present invention is useful as an easily openable heat seal material.
When used as an easy-open heat-seal material, it is often used in the form of being laminated on a base material, but since it has good adhesion to aluminum foil, it can be used as a sealing material for laminated materials containing aluminum foil. Especially useful.
As typical laminated material configurations, for example, the following can be illustrated, but of course, a part of them can be replaced with another material, or another material can be further laminated.

  That is, when the resin composition of the present invention is expressed as a sealing material, a printing protective layer / printing layer / aluminum foil / sealing material, biaxially oriented polyester / printing layer / adhesive / aluminum foil / sealing material, biaxially oriented polypropylene Examples of the laminated material include: / printing layer / adhesive / sealing material, printing protective layer / printing layer / paper / sealing material, polyethylene / printing layer / paper / polyethylene / aluminum foil / sealing material.

Examples and comparative examples are shown below to explain the effects of the present invention.
In addition, the raw material used in the Example etc. and the physical-property evaluation method of the obtained laminated lid | cover material are as follows.

1. Raw material resin (1) Copolymer A
The ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer comprises 80% by mass of ethylene units, 10% by mass of methacrylic acid units and 10% by mass of isobutyl acrylate units, and melt flow rate (MFR: JIS K7210-). 1999) was used with a copolymer of 35 g / 10 min.
(2) Copolymer B
The ethylene / (meth) acrylic acid ester copolymer is composed of 80% by mass of ethylene unit and 20% by mass of methyl acrylate unit, MFR = 8g / 10min, and melting point (JIS K7121) is 92 ° C. A polymer was used.
(3) Tackifying agent Alicyclic hydrocarbon resin having a ring-and-ball method softening point of 115 ° C. (intranuclear hydrogenated resin of aromatic hydrocarbon resin) (trade name: Alcon P-115, manufactured by Arakawa Chemical Co., Ltd.) ) Was used.

(4) Low density polyethylene (LDPE)
A low density polyethylene having an MFR of 4.5 g / 10 min and a density of 0.923 g / cm ³ was used.
(5) Low crystalline ethylene / α-olefin copolymer (Tuffmer)
A low crystalline ethylene / α-olefin copolymer (Mitsui Chemicals, trade name: Toughmer A4085) having an MFR of 3.6 g / 10 min was used.
(6) Other components Fatty acid amide was used as an anti-slip agent, and silica was used as an anti-blocking agent.

2. Physical properties of the laminated lid material The resin composition sample pellets of Examples and Comparative Examples were melt-extruded from a T-die (opening width: 500 mm) using a 65 mm diameter extruder at a die outlet resin temperature of 250 ° C. (set value), and prepared in advance. Processing speed for the aluminum foil surface of the three-layer flexible lid made of paper (basis weight 79 g / m ² ) / low density polyethylene film (thickness 15 μm) / aluminum foil (thickness 7 μm) Extrusion coating was performed under the conditions of 80 m / min and coating thickness of 25 μm to obtain a laminated lid material.
Table 1 shows the neck-in (NI) width (mm) and the drawdown / (DD) property of each resin composition under the above laminating conditions as indices of processability. The detailed evaluation method of NI and DD is as follows.
NI: T-die opening width 500 mm, resin thickness 20 μm, processing speed 80 m / min
Binaural value DD: Amount of extrusion during NI measurement (screw rotation speed)
Under constant conditions, the processing speed was gradually increased, and the processing speed at which film breakage occurred. The aluminum foil adhesion strength and heat seal strength of the heat sealing material layer of the obtained lid were measured by the following methods.

Moreover, the aluminum foil adhesive strength and heat seal strength of the heat seal material layer of the obtained cover material were measured by the following methods.
(1) Aluminum foil adhesive strength A sample 7 days after processing was measured under the conditions of a sample width of 15 mm, a peeling angle of 90 degrees, and a tensile speed of 300 mm / min.
(2) Evaluation of heat sealability for PSP (foamed styrene paper) and HIPS (impact-resistant polystyrene) container base material Using a heat sealer, the laminated lid material is used for the cup ramen PSP container base material and HIPS. The container base material was heat sealed with the strip-shaped sample, and the heat seal strength was measured.
Sealing conditions (vs. PSP): temperatures 120 ° C., 130 ° C., 140 ° C., 150 ° C. (vs. HIPS): temperatures 120 ° C., 140 ° C.
Pressure (both PSP and HIPS) was 0.1 MPa, time (both PSP and HIPS) was 1 second, and the feeling of peeling was: ○ Smooth Δ Slightly zipping × Zipping.

"Example 1"
A resin composition pellet consisting of 58.6 parts by mass of copolymer A, 40 parts by mass of copolymer B, 1.4 parts by mass of an additive component such as fatty acid amide, silica, etc. is subjected to extrusion coating processing under the above conditions to obtain a laminated lid material. Obtained.
The neck-in (NI) width at this time was 89 mm.
Table 1 summarizes the evaluation results such as the aluminum foil adhesive strength of the heat seal layer of the obtained lid material, the heat sealability to the container body substrate such as PSP, and the feel when peeled from the container body.
"Examples 2, 3, and 4"
The blending amounts of copolymer A and copolymer B in Example 1 were changed to the amounts shown in Table 1, respectively, and the tackifying resin (Arcon P-115) was shown in Table 1 respectively. A lid was prepared in the same manner as in Example 1 except that it was added, and evaluated in the same manner as in Example 1.
The results are summarized in Table 1.

"Comparative Example 1"
From 43 parts by weight of copolymer A, 16.5 parts by weight of copolymer B, 15 parts by weight of low density polyethylene, 10 parts by weight of low crystalline ethylene / α-olefin copolymer, 8 parts by weight of tackifying resin, and residual additive The resulting resin composition was treated in the same manner as in Example 1 to produce a lid, and evaluated in the same manner as in Example 1.
The results are summarized in Table 1.

Claims (8)

(A) ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer component or ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer and ethylene / (meth) acrylic acid copolymer Mixed component, 90-20 parts by mass, (B) ethylene / (meth) acrylic acid ester copolymer component, 10-80 parts by mass, and (C) tackifier resin component 0-20 parts by mass (provided (A ), (B), and (C) total component is 100 parts by mass), and the resin component is used as the ethylene / (meth) acrylate copolymer (B) as a melt flow rate (JIS K7210- 1999) is 0.1 to 500 g / 10 min, and a (meth) acrylic acid ester unit content is 5 to 30% by mass.   The ethylene / (meth) acrylic acid ester copolymer (B) has a melt flow rate of 0.5 to 150 g / 10 min and a (meth) acrylic acid ester unit content of 5 to 25% by mass. The resin composition according to claim 1.   (A) is composed of a mixed component of ethylene / (meth) acrylic acid / (meth) acrylic acid ester copolymer / ethylene / (meth) acrylic acid copolymer 100/0 to 60/40 by mass ratio. The resin composition according to claim 1. The resin composition according to any one of claims 1 to 3 , wherein 0.1 to 5 parts by mass of at least one of a slip agent and an antiblocking agent is blended with respect to 100 parts by mass of the resin component . Heat-sealing material made of a resin composition according to any one of claims 1 to 4. A laminate in which the heat seal material according to claim 5 is directly formed on an aluminum foil. The lid | cover material which uses the heat seal material of Claim 5 for a heat seal layer. A foamed polystyrene container or an impact-resistant polystyrene container using the heat seal material according to claim 5 for the heat seal layer.